Speed calculation device, speed estimation device, image forming device, and storage medium

ABSTRACT

A speed calculation device is provided. The generation component generates a plurality of pulse signals with different phases in accordance with rotation of a rotating body. The detection component detects rises and falls of respective pulses of the plurality of pulse signals generated by the generation component. The duration calculation component, each time a rise or fall is detected by the detection component, calculates a total duration of a pre-specified number of durations representing detection intervals of rises or falls detected prior to the rise or fall currently detected by the detection component. The speed calculation component calculates a speed relating to rotation of the rotating body on the basis of the total duration and a rotation angle of the rotating body that corresponds to one pulse of the pulse signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation-in-part (CIP) of prior U.S. patentapplication Ser. No. 12/465,100, the disclosure of which is incorporatedby reference herein. This application claims priority under 35 USC 119from Japanese Patent Applications No. 2008-319573 filed Dec. 16, 2008and No. 2009-204666 filed Sep. 4, 2009.

BACKGROUND

1. Technical Field of the Invention

The present invention relates to a speed calculation device, a speedestimation device, an image forming device, and a storage medium.

2. Related Art

Heretofore, an image recording device has been known that generates aprint clock on the basis of a pre-memorized print clock correctionamount and print clock modification amounts that are calculated fromamounts of variation of an angular speed, and a timing pulse generationdevice has been known that determines a droplet ejection period of adroplet ejection component on the basis of a pulse signal with a periodwhich is a division of a predicted period, for which a period of thepulse signal generated from the image recording device is predicted.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided aspeed calculation device including: a generation component thatgenerates a plurality of pulse signals with different phases inaccordance with rotation of a rotating body; a detection component thatdetects rises and falls of respective pulses of the plurality of pulsesignals generated by the generation component; a duration calculationcomponent that, each time a rise or fall is detected by the detectioncomponent, calculates a total duration of a pre-specified number ofdurations representing detection intervals of rises or falls detectedprior to the rise or fall currently detected by the detection component;and a speed calculation component that calculates a speed relating torotation of the rotating body on the basis of the total duration and arotation angle of the rotating body that corresponds to one pulse of thepulse signals.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a diagram illustrating structure of an image forming devicerelating to a first and seventh exemplary embodiments of the presentinvention;

FIG. 2 is a diagram illustrating structure of an inkjet ejectionaperture face side of an inkjet recording head relating to the first andseventh exemplary embodiments of the present invention;

FIG. 3 is a block diagram illustrating principal structures of anelectronic system of the image forming device relating to the first andthe seventh exemplary embodiments of the present invention;

FIG. 4 is schematic views illustrating an example of variations inconveyance speed associated with increasing rotation angle of an imageforming drum of the image forming device relating to the first andseventh exemplary embodiments of the present invention and an example ofa situation in which impact positions of ink droplets are altered due tothe variations;

FIG. 5 is a flowchart of image formation control processing that isexecuted by a CPU of the first exemplary embodiment of the presentinvention;

FIG. 6 is a flowchart of speed calculation processing that is executedby an FPGA of the first exemplary embodiment of the present invention;

FIG. 7A is an image forming device equipped only with a relatedtechnology;

FIG. 7B is an image forming device relating to the first exemplaryembodiment of the present invention;

FIG. 8 is a diagram for explaining a reduction in measurement accuracywhen a measurement period is shortened;

FIG. 9 is views of cases in which a single dot line is drawn in a mainscanning direction;

FIG. 10 is a flowchart of speed calculation processing that is executedby an FPGA of a second exemplary embodiment of the present invention;

FIG. 11 is a graph for describing details of the speed calculationprocessing of the second exemplary embodiment;

FIG. 12 is a graph for describing states of following of variations in aperipheral face speed V in the second exemplary embodiment;

FIG. 13 is a flowchart of image formation control processing that isexecuted by a CPU of a third exemplary embodiment;

FIG. 14 is a flowchart of speed calculation processing that is executedby an FPGA of the third exemplary embodiment;

FIG. 15 is a flowchart of speed calculation processing that is executedby an FPGA of a fourth exemplary embodiment;

FIG. 16 is a flowchart of speed calculation processing that is executedby an FPGA of a fifth exemplary embodiment;

FIG. 17 is a flowchart of speed calculation processing that is executedby an FPGA of a sixth exemplary embodiment;

FIG. 18 is a diagram illustrating another structure, which is an exampleto which the present invention is applicable;

FIG. 19 is a diagram for describing a variant example of an encoder;

FIG. 20 is a structural diagram illustrating structure of a rotaryencoder relating to a seventh exemplary embodiment;

FIG. 21 is a flowchart illustrating a flow of processing of an imageformation control processing program relating to the seventh exemplaryembodiment;

FIG. 22 is a flowchart illustrating a flow of processing of a speedestimation processing program relating to the seventh exemplaryembodiment;

FIG. 23 is a flowchart illustrating a flow of processing of a speedestimation processing program relating to an eighth exemplaryembodiment;

FIG. 24 is a flowchart illustrating a flow of processing of an imageformation control processing program relating to a ninth exemplaryembodiment;

FIG. 25 is a flowchart illustrating a flow of processing of a speedestimation processing program relating to the ninth exemplaryembodiment;

FIG. 26 is a flowchart illustrating a flow of processing of a speedestimation processing program relating to a tenth exemplary embodiment;

FIG. 27 is a flowchart illustrating a flow of processing of a speedestimation processing program relating to an eleventh exemplaryembodiment; and

FIG. 28 is a flowchart illustrating a flow of processing of a speedestimation processing program relating to a twelfth exemplaryembodiment.

DETAILED DESCRIPTION

Herebelow, the best embodiments for implementing the present inventionwill be described in detail with reference to the drawings.

First Exemplary Embodiment

Firstly, a first exemplary embodiment will be described. For the presentexemplary embodiment, a case is described in which the present inventionis applied to an inkjet-system image forming device. FIG. 1 is a diagramillustrating structure of an image forming device 10 relating to thepresent exemplary embodiment.

As shown in FIG. 1, a paper supply conveyance section 12 is provided atthe image forming device 10. The paper supply conveyance section 12supplies and conveys recording paper W, which is a recording medium. Ata downstream side of the paper supply conveyance section 12 in aconveyance direction of the recording paper W, a processing fluidapplication section 14, an image formation section 16, an ink dryingsection 18, an image fixing section 20 and an ejection conveyancesection 24 are provided along the conveyance direction of the recordingpaper W. The processing fluid application section 14 applies aprocessing fluid to a recording face (front face) of the recording paperW. The image formation section 16 forms an image on the recording faceof the recording paper W. The ink drying section 18 dries the image thathas been formed at the recording face. The image fixing section 20 fixesthe dried image to the recording paper W. The ejection conveyancesection 24 conveys the recording paper W to which the image has beenfixed to an ejection section 22.

The paper supply conveyance section 12 is provided with an accommodationsection 26 that accommodates the recording paper W. A motor 30 isprovided at the accommodation section 26. A paper supply apparatus isalso provided at the accommodation section 26. The recording paper W isfed out from the accommodation section 26 toward the processing fluidapplication section 14 by the paper supply apparatus.

The processing fluid application section 14 is provided with anintermediate conveyance drum 28A and a processing fluid application drum36. The intermediate conveyance drum 28A is rotatably disposed betweenthe accommodation section 26 and the processing fluid application drum36. A belt 32 spans between a rotation axle of the intermediateconveyance drum 28A and a rotation axle of the motor 30. Accordingly,rotary driving force of the motor 30 is transmitted to the intermediateconveyance drum 28A via the belt 32, and the intermediate conveyancedrum 28A rotates in the direction of circular arc arrow A.

A retention member 34 is provided at the intermediate conveyance drum28A. The retention member 34 nips a distal end portion of the recordingpaper W and retains the recording paper W. The recording paper W that isfed out from the accommodation section 26 to the processing fluidapplication section 14 is retained at a peripheral face of theintermediate conveyance drum 28A by the retention member 34, and isconveyed to the processing fluid application drum 36 by rotation of theintermediate conveyance drum 28A.

Similarly to the intermediate conveyance drum 28A, retention members 34are provided at intermediate conveyance drums 28B, 28C, 28D and 28E, theprocessing fluid application drum 36, an image forming drum 44, an inkdrying drum 56, an image fixing drum 62 and an ejection conveyance drum68, which are described below. The recording paper W is passed alongfrom upstream side drums to downstream side drums by these retentionmembers 34.

The processing fluid application drum 36 is linked with the intermediateconveyance drum 28A by gears, and receives rotary force and rotates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28A is taken up onto the processing fluid applicationdrum 36 by the retention member 34 of the processing fluid applicationdrum 36, and is conveyed in a state of being retained at a peripheralface of the processing fluid application drum 36.

At an upper portion of the processing fluid application drum 36, aprocessing fluid application roller 38 is disposed in a state oftouching against the peripheral face of the processing fluid applicationdrum 36. Processing fluid is applied to the recording face of therecording paper Won the peripheral face of the processing fluidapplication drum 36 by the processing fluid application roller 38. Thisprocessing fluid will react with the ink and coagulate a colorant(pigment), and promote separation of the colorant from a solvent.

The recording paper W to which the processing fluid has been applied bythe processing fluid application section 14 is conveyed to the imageformation section 16 by rotation of the processing fluid applicationdrum 36.

The image formation section 16 is provided with the intermediateconveyance drum 28B and the image forming drum 44. The intermediateconveyance drum 28B is linked with the intermediate conveyance drum 28Aby gears, and receives rotary force and rotates.

The recording paper W that has been conveyed by the processing fluidapplication drum 36 is taken up onto the intermediate conveyance drum28B by the retention member 34 of the intermediate conveyance drum 28Bof the image formation section 16, and is conveyed in a state of beingretained at a peripheral face of the intermediate conveyance drum 28B.

The image forming drum 44, which is a rotating body, is linked with theintermediate conveyance drum 28A by gears, and receives rotary force androtates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28B is taken up onto the image forming drum 44 by theretention member 34 of the image forming drum 44, and is conveyed in astate of being retained at a peripheral face of the image forming drum44.

Above the image forming drum 44, a head unit 46 is disposed close to theperipheral face of the image forming drum 44. The head unit 46 isprovided with four inkjet recording heads 48, corresponding to each ofthe four colors yellow (Y), magenta (M), cyan (C) and black (K). Theseinkjet recording heads 48 are arranged along the peripheral direction ofthe image forming drum 44, and form an image by ejecting ink dropletsfrom nozzles 48 a, which will be described later, synchronously withclock signals, which will be described later, such that the ink dropletsare superposed with a film of the processing fluid that has been formedon the recording face of the recording paper W by the processing fluidapplication section 14.

The image forming drum 44 is provided with a rotary encoder 52. Therotary encoder 52 relating to the present exemplary embodiment, inaccordance with rotation of the image forming drum 44, generates andoutputs plural pulse signals with respectively different phases. Onepulse of the pulse signals corresponds to a pre-specified rotation angleθ₀ (for example, 1.257 milliradians). In the present exemplaryembodiment, the rotary encoder 52 generates two pulse signals, of phaseA and phase B.

The recording paper W on which the image has been formed at therecording face by the image formation section 16 is conveyed to the inkdrying section 18 by rotation of the image forming drum 44.

The ink drying section 18 is provided with the intermediate conveyancedrum 28C and the ink drying drum 56. The intermediate conveyance drum28C is linked with the intermediate conveyance drum 28A by gears, andreceives rotary force and rotates.

The recording paper W that has been conveyed by the image forming drum44 is taken up onto the intermediate conveyance drum 28C by theretention member 34 of the intermediate conveyance drum 28C, and isconveyed in a state of being retained at a peripheral face of theintermediate conveyance drum 28C.

The ink drying drum 56 is linked with the intermediate conveyance drum28A by gears, and receives rotary force and rotates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28C is taken up onto the ink drying drum 56 by theretention member 34 of the ink drying drum 56, and is conveyed in astate of being retained at a peripheral face of the ink drying drum 56.

Above the ink drying drum 56, a hot air heater 58 is disposed close tothe peripheral face of the ink drying drum 56. Excess solvent in theimage that has been formed on the recording paper W is removed by hotair from the hot air heater 58. The recording paper W at which the imageon the recording face has been dried by the ink drying section 18 isconveyed to the image fixing section 20 by rotation of the ink dryingdrum 56.

The image fixing section 20 is provided with the intermediate conveyancedrum 28D and the image fixing drum 62. The intermediate conveyance drum28D is linked with the intermediate conveyance drum 28A by gears, andreceives rotary force and rotates.

The recording paper W that has been conveyed by the ink drying drum 56is taken up onto the intermediate conveyance drum 28D by the retentionmember 34 of the intermediate conveyance drum 28D, and is conveyed in astate of being retained at a peripheral face of the intermediateconveyance drum 28D.

The image fixing drum 62 is linked with the intermediate conveyance drum28A by gears, and receives rotary force and rotates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28D is taken up onto the image fixing drum 62 by theretention member 34 of the image fixing drum 62, and is conveyed in astate of being retained at a peripheral face of the image fixing drum62.

At an upper portion of the image fixing drum 62, a fixing roller 64,which has a heater thereinside, is disposed in a state of abuttingagainst a peripheral face of the image fixing drum 62. The recordingpaper W retained at the peripheral face of the image fixing drum 62 isheated by the heater in a state in which the recording paper W ispressing against the fixing roller 64, and thus colorant in the imageformed at the recording face of the recording paper W is fused to therecording paper W, and the image is fixed to the recording paper W. Therecording paper W to which the image has been fixed by the image fixingsection 20 is conveyed to the ejection conveyance section 24 by rotationof the image fixing drum 62.

The ejection conveyance section 24 is provided with the intermediateconveyance drum 28E and the ejection conveyance drum 68. Theintermediate conveyance drum 28E is linked with the intermediateconveyance drum 28A by gears, and receives rotary force and rotates.

The recording paper W that has been conveyed by the image fixing drum 62is taken up onto the intermediate conveyance drum 28E by the retentionmember 34 of the intermediate conveyance drum 28E, and is conveyed in astate of being retained at a peripheral face of the intermediateconveyance drum 28E.

The ejection conveyance drum 68 is linked with the intermediateconveyance drum 28A by gears, and receives rotary force and rotates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28E is taken up onto the ejection conveyance drum 68 bythe retention member 34 of the ejection conveyance drum 68, and isconveyed toward the ejection section 22 in a state of being retained ata peripheral face of the ejection conveyance drum 68.

FIG. 2 is a diagram illustrating structure of an inkjet ejectionaperture face side of the inkjet recording head 48 relating to thepresent exemplary embodiment.

As shown in FIG. 2, a plurality of the nozzles 48 a, which respectivelyeject ink droplets, are formed in a face 90 of the inkjet recording head48 that opposes the peripheral face of the image forming drum 44. Theinkjet recording head 48 has a structure in which the plural nozzles 48a are arranged in a two-dimensional pattern (a staggered matrix form inthe present exemplary embodiment) without overlapping in the directionof conveyance of the recording paper W by the image forming drum 44(i.e., a sub-scanning direction). Thus, an increase in density of aneffective nozzle spacing (projected nozzle pitch) as projected so as tolie along a head length direction (a direction orthogonal to thedirection of conveyance of the recording paper W by the image formingdrum 44 (which is below referred to simply as the conveyance direction))is achieved.

Here, in the inkjet recording head 48 relating to the present exemplaryembodiment, the plural nozzles 48 a are arranged in two rows withrespect to the sub-scanning direction and the two rows are separated byL mm in the sub-scanning direction. Hereafter, the plural nozzles 48 ain the row at the conveyance direction upstream side are referred to asnozzle group A, and the plural nozzles 48 a in the row at the conveyancedirection downstream side are referred to as nozzle group B.

FIG. 3 is a block diagram illustrating principal structures of anelectronic system of the image forming device 10 relating to the presentexemplary embodiment.

The image forming device 10 is structured to include a CPU (centralprocessing unit) 70, a ROM (read-only memory) 72, a RAM (random accessmemory) 74, an NVM (non-volatile memory) 76, a UI (user interface) panel78, an FPGA (field-programmable gate array) 79 and a communication I/F(communication interface) 80. In the present exemplary embodiment, anapparatus including this computer and the rotary encoder 52 serves as aspeed calculation device that features a function of calculating a speedrelating to rotation of the image forming drum 44 serving as therotating body.

The CPU 70 administers operations of the image forming device 10 as awhole. The CPU 70 reads a program from the ROM 72 and executes imageformation control processing.

The ROM 72 serves as a memory component and memorizes beforehand: aprogram for executing the image formation control processing thatcontrols operations of the image forming device 10, which is describedin detail hereafter; the rotation angle θ₀ that is represented by onepulse of the pulse signals outputted from the rotary encoder 52; adistance between the peripheral face of the image forming drum 44(peripheral face of the rotating body) and the axial center of the imageforming drum 44 (referred to hereafter in the present exemplaryembodiment as distance R₀); a distance between neighboring dots (herein,between centers of the dots; referred to hereafter in the firstexemplary embodiment as distance X₀); and various parameters and thelike. In the present exemplary embodiment, a radius of the image formingdrum 44 is employed as the pre-specified distance R₀ but this is notlimiting and another value may be employed.

The RAM 74 is used as a work area during execution of various programsand the like. The NVM 76 memorizes various kinds of information thatneed to be retained when a power switch of the device is turned off.

The UI panel 78 is structured by a touch panel display, in which atransparent touch panel is superposed on a display, or the like. The UIpanel 78 displays various kinds of information at a display screen ofthe display, and inputs required information, instructions and the likein accordance with a user touching the touch panel.

The FPGA 79 reads a program from the ROM 72 and executes the speedcalculation processing.

The communication interface 80 is connected with a terminal device 82,such as a personal computer or the like, and receives image informationrepresenting an image to be formed at the recording paper W and variousother kinds of information from the terminal device 82.

The CPU 70, the ROM 72, the RAM 74, the NVM 76, the UI panel 78, theFPGA 79 and the communication interface 80 are connected to one anothervia a system bus. Therefore, the CPU 70 may implement each of access tothe ROM 72, the RAM 74 and the NVM 76, display of various kinds ofinformation at the UI panel 78, acquisition of details of controlinstructions from users from the UI panel 78, reception of various kindsof information from the terminal device 82 via the communicationinterface 80, and control of the FPGA 79.

The image forming device 10 is further provided with a recording headcontroller 84 and a motor controller 86.

The recording head controller 84 controls operations of the inkjetrecording head 48 in accordance with instructions from the CPU 70. Themotor controller 86 controls operations of the motor 30.

The recording head controller 84 and the motor controller 86 are alsoconnected to the above-mentioned system bus. Thus, the CPU 70 mayimplement control of operations of the recording head controller 84 andthe motor controller 86.

The aforementioned rotary encoder 52 is also connected to theaforementioned system bus. Thus, the CPU 70 may receive the plural pulsesignals generated by the rotary encoder 52.

Next, operation of the image forming device 10 relating to the presentexemplary embodiment will be described.

In the image forming device 10 relating to the present exemplaryembodiment, recording paper W is fed out from the accommodation section26 to the intermediate conveyance drum 28A by the paper supplyapparatus, the recording paper W is conveyed via the intermediateconveyance drum 28A, the processing fluid application drum 36 and theintermediate conveyance drum 28B to the image forming drum 44, and isretained at the peripheral face of the image forming drum 44. Then, inkdroplets are ejected at the recording paper W on the image forming drum44 from the nozzles 48 a of the inkjet recording head 48 in accordancewith image information. Thus, an image represented by the imageinformation is formed on the recording paper W.

Now, a conveyance speed of the recording paper W that is retained at theperipheral face of the image forming drum 44 varies as is shown by theexample in the graph of FIG. 4, for reasons such as variations inmeshing and loading of the driving system gears and variations in speedof the motor itself The vertical axis of the graph in FIG. 4 shows theconveyance speed of the recording paper W at the image forming drum 44,and the horizontal axis shows the rotation angle of the image formingdrum 44 from the pre-specified reference position. The broken linecircles in the image in FIG. 4 illustrate an example of impact positionsof ink droplets ejected from the nozzles 48 a in a case in which theconveyance speed of the recording paper W is constant at a speed V. Thesolid line circles in the image in FIG. 4 illustrate an example ofimpact positions of the ink droplets ejected from the nozzles 48 a in acase in which there are variations in speed of the recording paper W.

In conditions in which the conveyance speed of the recording paper W atthe image forming drum 44 varies in this manner, clock signals ofconstant frequency are outputted to the inkjet recording heads 48, andwhen the ink droplets are ejected from the nozzles 48 a at the inkjetrecording heads 48 synchronously with these clock signals, an image thatis formed by the ink droplets is deformed as shown in the example inFIG. 4.

Now, in order to suppress deformation of images due to speed variations,detecting or calculating the conveyance speed of the recording paper Wand altering the frequency of the clock signals in accordance with theconveyance speed may be considered. In order to detect or calculate theconveyance speed of the recording paper W accurately, it is necessary toimprove tracking of variations of the rotation speed of the imageforming drum 44. Employing an encoder that generates pulse signals withhigh frequency for the rotary encoder 52 may be considered for improvingtracking of variations in the rotation speed of the image forming drum44. This is because it is thought that, when the rotary encoder 52 thatgenerates pulse signals with high frequency is employed, a detectioninterval of the rotation speed of the image forming drum 44 is shorterand tracking of variations of the rotation speed of the image formingdrum 44 improves. However, when the frequency is higher, a period of thepulse signals that are outputted from the rotary encoder 52 is shorterand measurement accuracy falls.

Accordingly, in the image forming device 10 relating to the presentexemplary embodiment, in order to suppress deformation of an image dueto variations in speed, the speed calculation processing is executed inorder to improve tracking of variations in a speed relating to rotationof the image forming drum 44 and to calculate the speed relating torotation of the image forming drum 44 with high accuracy.

Next, referring to FIG. 5, the image formation control processing thatis executed by the CPU 70 of the image forming device 10 will bedescribed. In the present exemplary embodiment, the image formationcontrol processing is executed when an instruction for execution of theimage formation processing, for forming an image at the recording paperW, and image information of an image formation subject are inputted fromthe terminal device 82 via the communication I/F 80 and the CPU 70determines that this execution instruction and image information havebeen inputted.

Firstly, in step 100, an instruction to commence execution of the speedcalculation processing is outputted to the FPGA 79, and the FPGA 79performs control so as to commence execution of the speed calculationprocessing.

Now the speed calculation processing that is executed by the FPGA 79will be described referring to FIG. 6.

Firstly, in step 200, the rotation angle θ₀ and the distance R₀ are readout from the ROM 72.

Then, in step 202, the motor controller 86 is controlled such that theimage forming drum 44 commences rotary driving. Hence, the image formingdrum 44 commences rotary driving due to the motor controller 86controlling the motor 30 so as to commence the rotary driving.

Next, in step 204, the processing waits until the image forming drum 44reaches a predetermined rotation speed (for example, 500 mm/s). Here,the judgement of whether or not the image forming drum 44 has reachedthe predetermined rotation speed is determined on the basis of pulsesignals from the rotary encoder 52. When it is judged in step 204 thatthe image forming drum 44 has reached the predetermined rotation speed,the processing advances to the next step 206.

Then, in step 206, variables—a variable i, a variable T0, a variable T1,a variable T2, a variable T3 and a variable E1—are initialized bysetting values of the variables to zero.

Next, in step 208, a timer is started for measuring a duration from aprevious detection in the processing of step 210, details of which aredescribed below, until a next detection. Accordingly, the duration ismeasured in unit time intervals (for example, of 10 ns (nanoseconds)),and the duration that is measured each time the measured duration isupdated is put into the variable i. More specifically, the duration iscomputed from a clock count of a counter installed at the FPGA 79.

Then, in step 210, rises and falls of the respective pulses of the twopulse signals of phase A and phase B outputted from the rotary encoder52 are detected for. Accordingly, when a pulse of either of the twopulse signals with phase A and phase B rises, the rise of the pulse ofthat signal is detected, and when a pulse of either of the two pulsesignals with phase A and phase B falls, the fall of the pulse of thatsignal is detected.

Next, in step 212, it is judged whether or not a rise of a pulse hasbeen detected or a fall of a pulse has been detected in step 210. If itis judged in step 212 that a pulse rise has been detected or a pulsefall has been detected in step 210, the processing advances to the nextstep 214. On the other hand, if it is judged in step 212 that no pulserise has been detected and no pulse fall has been detected in step 210,the processing returns to step 210, and rises and falls of therespective pulses of the two pulse signals with phase A and phase Boutputted from the rotary encoder 52 are again detected for.

In step 214, the value of variable T0 is updated by putting the value ofvariable T1 into variable T), the value of variable T1 is updated byputting the value of variable T2 into variable T1, the value of variableT2 is updated by putting the value of variable T3 into variable T2, andthe value of variable T3 is updated by putting the value of variable iinto variable T3. Then the value of variable E1 is updated by puttingthe sum of the value of variable T0, the value of variable T1, the valueof variable T2 and the value of variable T3 (T0+T1+T2+T3) into variableE1. Then, initialization is performed by stopping the timer that startedin step 208 and setting the value of variable i to zero. Here, if thedetection of a pulse rise or detection of a pulse fall in the mostrecent processing of step 210 is a first (initial) detection, the valueof variable i that has been put into variable T3 in the present step 214is the duration from the present speed calculation processing startinguntil a first detection. If the detection of a pulse rise or detectionof a pulse fall in the most recent processing of step 210 is a second orsubsequent detection, this value of variable i is the duration from theprevious detection by the processing of step 210 to the currentdetection by the processing of step 210. That is, in step 214, each timea rise or fall is detected in step 210, the duration E1 is calculated,which is a total of durations (T0, T1, T2 and T3) representing detectionintervals of the rises and falls that have been detected in apre-specified number (T0 to T3 being four thereof) prior to the currentrise or fall detected in step 210.

Then, in step 216, by determining whether or not all the values ofvariable T0, variable T1, variable T2 and variable T3 are greater thanzero, it is determined whether or not information that will be requiredwhen calculating a speed in step 218, details of which are describedbelow, is all present.

In step 216, if it is judged that there is a variable among all thevariables of variable T0, variable T1, variable T2 and variable T3 whosevalue is zero, it is determined that all the information that would berequired when calculating the speed in step 218 whose details aredescribed below is not present, and the processing returns to step 208.On the other hand, if it is judged that the values of all the variablesof variable T0, variable T1, variable T2 and variable T3 are greaterthan zero, it is determined that all the information that will berequired when calculating the speed in step 218 whose details aredescribed below is present, and the processing advances to the next step218.

In step 218, a speed relating to rotation of the image forming drum 44is calculated on the basis of the total duration E1 computed in step 214and the rotation angle θ₀ of the image forming drum 44 that correspondsto one pulse of the pulse signals. More specifically, in step 218, aperipheral face speed V of the image forming drum 44 is calculated bydividing a movement distance (R₀θ₀) of the peripheral face of the imageforming drum 44 through the rotation angle θ₀ by the total duration E1,as in the following equation (1).V=(R ₀θ₀)/E1  Equation (1)

Then, in step 220, the value of the peripheral face speed V calculatedin step 218 is outputted (reported) to the CPU 70.

Next, in step 222, it is judged whether or not an instruction to stopexecution of the speed calculation processing has been received from theCPU 70. If it is judged in step 222 that an instruction to stopexecution of the speed calculation processing has not been received, theprocessing returns to step 208. On the other hand, if it is judged instep 222 that an instruction to stop execution of the speed calculationprocessing has been received, the present speed calculation processingends.

Now the description of the image formation control processing shown inFIG. 5 is resumed. In the next step 102, it is determined whether or nota value of the peripheral face speed V has been received from the FPGA79. The determination processing of step 102 is repeated until receptionis determined. When reception is determined in step 102, the processingadvances to the next step 104.

Then, in step 104, the distance X₀ is read from the ROM 72, and theperipheral face speed calculated by the speed calculation processing isused to calculate, with the following equation (2), a period P of theclock signal that prescribes timings of ejections of ink droplets fromthe nozzles 48 a.

$\begin{matrix}{P = {{X_{0}/V}\mspace{14mu} = {X_{0}E\;{1/\left( {R_{0}\theta_{0}} \right)}}}} & {{Equation}\mspace{14mu}(2)}\end{matrix}$

Then, in step 106, a clock signal with the calculated period P isgenerated and instructions to eject ink droplets from the nozzles 48 a,synchronously with this clock signal, are outputted to the recordinghead controller 84 in accordance with the received image information.Hence, the recording head controller 84 controls the nozzles 48 a so asto eject droplets in accordance with the received image informationsynchronously with this clock signal. Thus, an image represented by theimage information is formed at the recording face of the recording paperW without being affected by changes in the conveyance speed of therecording paper W.

Next, in step 108, it is judged whether or not image formation with thereceived image information has ended. If this judgement is negative, theprocessing returns to step 102. On the other hand, if the judgement instep 108 is positive, the processing advances to the next step 110. Instep 110, an instruction to stop execution of the speed calculationprocessing is outputted to the FPGA 79. Then, the image formationcontrol processing ends.

The speed calculation device of the image forming device 10 of thepresent exemplary embodiment as described above is constituted toinclude the rotary encoder 52 to serve as a generation component thatgenerates plural pulse signals with different phases (in the presentexemplary embodiment, the pulse signals with phase A and phase B) inaccordance with rotation of the image forming drum 44 which serves asthe rotating body that rotates. The speed calculation device of theimage forming device 10 of the present exemplary embodiment detectsrises and falls of respective pulses of the plural pulse signalsgenerated by the rotary encoder 52 in step 210. Then the speedcalculation device of the image forming device 10 of the presentexemplary embodiment, each time a rise or fall is detected in step 210,calculates, in step 214, the total duration E1 of durations (T0, T1, T2and T3) representing detection intervals of the rises and falls detectedin the pre-specified number (T0, T1, T2 and T3 being four) prior to thecurrent rise or fall detected in step 210. Hence, the speed calculationdevice of the image forming device 10 of the present exemplaryembodiment calculates a speed relating to rotation of the image formingdrum 44 in step 218 on the basis of the total duration E1 and therotation angle θ₀ of the image forming drum 44 that corresponds to onepulse of the pulse signals generated by the rotary encoder 52. Morespecifically, the peripheral face speed V of the image forming drum 44is calculated in step 218 by dividing the movement distance (R₀θ₀) ofthe peripheral face of the image forming drum 44, through the rotationangle θ₀ of the image forming drum 44 that corresponds to one pulse ofthe pulse signals, by the total duration E1. Further, the image formingdevice 10 of the present exemplary embodiment is constituted to includeinkjet recording heads 48 in which the nozzles 48 a that serve as pluralimage forming elements, which form dots that respectively constitute animage at a predetermined surface synchronously with a clock signal, arearranged. The image forming drum 44 rotates with the peripheral facethereof opposing the plural nozzles 48 a in the state in which therecording paper W, which serves as the recording medium, is retained atthe peripheral face of the image forming drum 44, such that the image isformed at the recording paper W by the respective plural nozzles 48 a.The image forming device 10 of the present exemplary embodimentcalculates a period P of the clock signal in step 104 on the basis ofthe peripheral face speed V calculated by the speed calculation deviceand the distance X₀ between neighboring dots. Accordingly, if, forexample, tracking of variations of the peripheral face speed V of animage forming drum as represented by a speed 62, which is detected onthe basis of pulse signals from a rotary encoder by an image formingdevice that is provided only with a related technology, for an actualspeed V shown in FIG. 7A (61) is compared with tracking of variations ofthe peripheral face speed V of the image forming drum 44 as representedby a speed 64, which is detected on the basis of plural pulse signalsfrom the rotary encoder 52 by the speed calculation device of the imageforming device 10 of the present exemplary embodiment, for an actualspeed V shown in FIG. 7B (63), it is understood that the image formingdevice 10 of the present exemplary embodiment is more excellent after atime t₆.

In the above description, an example is described of calculating theperipheral face speed using the total duration E1 of the pre-specifiednumber (T0, T1, T2 and T3 being four) of durations (T0, T1, T2 and T3)representing detection intervals of rises and falls that are detected. Amethod that gets closer to variations of the actual peripheral facespeed of the image forming drum 44 by calculating the peripheral facespeed using the durations that represent detection intervals (T0, T1, T2and T3) may be considered. However, with such a method, accuracy of thecalculated peripheral face speed falls for the reason described below.This reason will be described using FIG. 8. FIG. 8 shows pulses of thepulse signals with phase A and phase B that are outputted from therotary encoder and thresholds (limits) of FPGA edge detection (detectionof a rise or fall). The output pulses of the rotary encoder are slightlysloped. If, for example, the threshold is lower than a midpoint of thepulse voltages as shown in FIG. 8, then rise-to-fall intervals will beshorter than fall-to-rise intervals. In addition, phases of phase A andphase B depend on positional accuracy of detectors (which here aredetectors of the rotary encoder). Therefore, if one pulse is dividedinto four, the phase differences will not be precisely 90°. That is, asingle pulse will not be strictly equally divided. Therefore, if theperiod P of a clock signal is calculated with the above-mentioned methodand the clock signal with the calculated period P is used during imageformation, accuracy will fall. For this reason, it is preferable to usethe total duration E1 to calculate the peripheral face speed V.

With the image forming device equipped with the related technology andthe image forming device 10 of the present exemplary embodiment, asshown in FIG. 9, a single dot line (single line) was drawn in the mainscanning direction and an offset of the dots δ was measured. Measurementresults are shown below in table 1.

TABLE 1 Dot offset δ Phase A rise (conventional) 3.3 μm Detecting risesand falls of phases A and B 2.2 μm

As shown in table 1, with the image forming device equipped with therelated technology, the dot offset δ was 3.3 μm and with the imageforming device 10 of the present exemplary embodiment, the dot offset δwas 2.2 μm.

Conditions here are as shown below.

Conditions

-   Rotation speed V₀: 200 mm/s-   Printing drum (image forming drum) radius R: 100 mm-   Speed variation ΔV: 1%-   Speed variation frequency: 5 Hz-   2-dimensional head nozzle spacing L: 4 mm-   Rotary encoder: 500 pulses/revolution-   FPGA clock frequency: 20 MHz

Second Exemplary Embodiment

Next, a second exemplary embodiment will be described. Portions of thepresent exemplary embodiment that are the same as in the first exemplaryembodiment are assigned the same reference numerals and will not bedescribed.

In the first exemplary embodiment, an example is described in which theprogram for executing the speed calculation processing shown in FIG. 6is memorized in the ROM 72, and the FPGA 79 reads the program from theROM 72 and executes the speed calculation processing shown in FIG. 6. Inthe present exemplary embodiment, a program for executing speedcalculation processing shown in FIG. 10 is memorized in the ROM 72 inadvance, and the FPGA 79 reads this program from the ROM 72 and executesthe speed calculation processing shown in FIG. 10.

Now the speed calculation processing that is executed by the FPGA 79 ofthe present exemplary embodiment will be described referring to FIG. 10.

Steps 200, 202 and 204 (steps 200 to 204) are the same as in the firstexemplary embodiment, so will not be described. In the present exemplaryembodiment, after step 204 the processing advances to step 207. In step207, variables—a variable i, a variable T0, a variable T1, a variableT2, a variable T3, a variable T4, a variable E1 and a variable E2—areinitialized by setting the values of the variables to zero.

Next, in step 208, the same as in the first exemplary embodiment, atimer is started for measuring a duration from a previous detection inthe processing of step 210, details of which are described below, untila next detection.

Then, in step 210, the same as in the first exemplary embodiment, risesand falls of the respective pulses of the two pulse signals of phase Aand phase B outputted from the rotary encoder 52 are detected for.

Next, in step 212, the same as in the first exemplary embodiment, it isjudged whether or not a rise of a pulse has been detected or a fall of apulse has been detected in step 210. If it is judged in step 212 that apulse rise has been detected or a pulse fall has been detected in step210, the processing advances to the next step 215. On the other hand, ifit is judged in step 212 that no pulse rise has been detected and nopulse fall has been detected in step 210, the processing returns to step210, and rises and falls of the respective pulses of the two pulsesignals with phase A and phase B outputted from the rotary encoder 52are again detected for.

In step 215, the value of variable T0 is updated by putting the value ofvariable T1 into variable T0, the value of variable T1 is updated byputting the value of variable T2 into variable T1, the value of variableT2 is updated by putting the value of variable T3 into variable T2, thevalue of variable T3 is updated by putting the value of variable T4 intovariable T3, and the value of variable T4 is updated by putting thevalue of variable i into variable T4. Then the value of variable E1 isupdated by putting the sum of the value of variable T0, the value ofvariable T1, the value of variable T2 and the value of variable T3(T0+T1+T2+T3) into variable E1, and the value of variable E2 is updatedby putting the sum of the value of variable T1, the value of variableT2, the value of variable T3 and the value of variable T4 (T1+T2+T3+T4)into variable E2. Then, initialization is performed by stopping thetimer that started in step 208 and setting the value of variable i tozero. Here, if the detection of a pulse rise or detection of a pulsefall in the most recent processing of step 210 is a first (initial)detection, the value of variable i that has been put into variable T4 inthe present step 215 is the duration from the present speed calculationprocessing starting until a first detection. If the detection of a pulserise or detection of a pulse fall in the most recent processing of step210 is a second or subsequent detection, this value of variable i is theduration from the previous detection by the processing of step 210 tothe current detection by the processing of step 210. That is, in step215, each time a rise or fall is detected in step 210, the duration E1is calculated, which is a total of durations (T0, T1, T2 and T3)representing detection intervals of the rises and falls that have beendetected in a pre-specified number (T0 to T3 being four thereof) priorto the current rise or fall detected in step 210, in addition to whichthe duration E2 is calculated, which is a total of durations (T1, T2, T3and T4) representing detection intervals of the rises and falls whichhave been detected in a pre-specified first number (T1 to T4 being fourthereof) prior to the current rise or fall detected in step 210.

Then, in step 217, by determining whether or not all the values ofvariable T0, variable T1, variable T2, variable T3 and variable T4 aregreater than zero, it is determined whether or not information that willbe required when calculating a speed in step 221, details of which aredescribed below, is all present.

In step 217, if it is judged that there is a variable among all thevariables of variable T0, variable T1, variable T2, variable T3 andvariable T4 whose value is zero, it is determined that all theinformation that would be required when calculating the speed in step221 whose details are described below is not present, and the processingreturns to step 208. On the other hand, if it is judged that the valuesof all the variables of variable T0, variable T1, variable T2, variableT3 and variable T4 are greater than zero, it is determined that all theinformation that will be required when calculating the speed in step 221whose details are described below is present, and the processingadvances to the next step 219.

In step 219, for each of the total durations E1 and E2 that have beencalculated in step 215, control is performed so as to memorize the totaldurations E1 and E2 in the NVM 76, which serves as a memory component,in a pre-specified number (E1 and E2 being two in the present exemplaryembodiment; this number is referred to as a third number) to serve as ahistory. Accordingly, the total durations E1 and E2 are memorized in theNVM 76.

Then, in step 221, a speed relating to rotation of the image formingdrum 44 is calculated on the basis of, of the third number of totaldurations E1 and E2 memorized in the NVM 76, a second number of totaldurations E1 and E2 (E1 and E2 being two in the present exemplaryembodiment) and the rotation angle θ₀ of the image forming drum 44 thatcorresponds to one pulse of the pulse signal. More specifically, in step221 a duration E, for calculating the speed relating to rotation of theimage forming drum 44 (the peripheral face speed V in the presentexemplary embodiment) that is to be calculated a next time, is estimatedby linear extrapolation based on, of the third number of total durationsE1 and E2 memorized in the NVM 76, the second number of total durationsE1 and E2 (E1 and E2 being two in the present exemplary embodiment), andthe peripheral face speed V of the image forming drum 44 is calculatedby dividing the movement distance (R₀θ₀) of the peripheral face of theimage forming drum 44 through the rotation angle θ₀ by the estimatedduration E, as in the following equation (3).V=(R ₀θ₀)/E  Equation (3)

Then the processing advances to step 220 and subsequent processing thesame as in the first exemplary embodiment is performed.

Now, the processing of step 221 will be more specifically described withreference to FIG. 11.

As shown in FIG. 11, a period (total duration) represented by the mostrecent pulse signals from the rotary encoder 52 is E2, and a period(total duration) one step prior thereto is E1. A speed V1 (=(R₀θ₀)/E1)calculated with E1 is an average speed over t₁-t₅, and a speed V2(=(R₀θ₀)/E2) calculated with E2 is an average speed over t₂-t₆. Thespeed V1 and the speed V2 correspond to speeds at times t₃ and t₄,respectively.

The speed to be estimated from E1 and E2 here is the speed V in theinterval t₆-t₇. Assuming that intervals t_(i)-t_(i+1) are substantiallyequal intervals, the speed V at an intermediate point during t₆-t₇ isrepresented by the following equation (4) according to linearextrapolation.

$\begin{matrix}{V = {{\left( {R_{0}\theta_{0}} \right)/\left( {{3.5*E\; 2} - {2.5*E\; 1}} \right)}\mspace{20mu} = {2{\left( {R_{0}\theta_{0}} \right)/\left( {{7*E\; 2} - {5*E\; 1}} \right)}}}} & {{Equation}\mspace{14mu}(4)}\end{matrix}$

Herein, “*” is a symbol representing multiplication. That is, “A*B”represents the product of A and B.

States of tracking of variations of the peripheral face speed V in sucha case are as shown in FIG. 12.

Then the processing advances to step 220 and subsequent processing thesame as in the first exemplary embodiment is performed.

Here, the period P of the clock signal that is calculated in step 102 ofthe present exemplary embodiment is as in the following equation (5).

$\begin{matrix}{P = {{X_{0}/V}\mspace{14mu} = {{{X_{0}\left( {{3.5*E\; 2} - {2.5*E\; 1}} \right)}/\left( {R_{0}\theta_{0}} \right)}\mspace{14mu} = {{{X_{0}\left( {{7*E\; 2} - {5*E\; 1}} \right)}/2}\left( {R_{0}\theta_{0}} \right)}}}} & {{Equation}\mspace{14mu}(5)}\end{matrix}$

In the above description, a speed at an intermediate point during t₆-t₇is estimated. However, a speed at t₆ may be estimated to serve as arepresentative speed V. In step 221 in this case, the total duration Ecalculated for the next time thereafter is estimated by linearextrapolation based on, of the pre-specified third number of totaldurations E1 and E2 memorized in the NVM 76, the second number of totaldurations E1 and E2 (E1 and E2 being two in the present exemplaryembodiment), and the peripheral face speed V of the image forming drum44 is calculated by dividing the movement distance (R₀θ₀) of theperipheral face of the image forming drum 44 through the rotation angleθ₀ by this estimated total duration E. The period P of the clock signalthat is calculated in step 102 in this case is represented by thefollowing equation (6).

$\begin{matrix}{P = {{X_{0}/V}\mspace{14mu} = {{X_{0}\left( {{3*E\; 2} - {2*E\; 1}} \right)}/\left( {R_{0}\theta_{0}} \right)}}} & {{Equation}\mspace{14mu}(6)}\end{matrix}$

Similarly, a speed at t₇ may be estimated to serve as a representativespeed V. In step 221 in this case, the total duration E calculated forthe next time thereafter is estimated by linear extrapolation based on,of the pre-specified third number of total durations E1 and E2 memorizedin the NVM 76, the second number of total durations E1 and E2 (two of E1and E2 in the present exemplary embodiment), and the peripheral facespeed V of the image forming drum 44 is calculated by dividing themovement distance (R₀θ₀) of the peripheral face of the image formingdrum 44 through the rotation angle θ₀ by this estimated total durationE. The period P of the clock signal that is calculated in step 102 inthis case is represented by the following equation (7).

$\begin{matrix}{P = {{X_{0}/V}\mspace{20mu} = {{X_{0}\left( {{4*E\; 2} - {3*E\; 1}} \right)}/\left( {R_{0}\theta_{0}} \right)}}} & {{Equation}\mspace{14mu}(7)}\end{matrix}$

With the image forming device equipped with the related technology andthe image forming device 10 of the present exemplary embodiment, asingle dot line (single line) was drawn in the main scanning direction,as shown in FIG. 9, and an offset of the dots δ was measured.Measurement results are shown below in table 2.

TABLE 2 Dot offset δ Phase A rise (conventional) 3.3 μm Detecting risesand falls of phases A and B + 1.5 μm extrapolation

As shown in table 2, with the image forming device equipped with therelated technology, the dot offset δ was 3.3 μm, and with the imageforming device 10 of the present exemplary embodiment, the dot offset δwas 1.5 μm.

Conditions in this case are the same as those described for table 1.

The speed calculation device of the image forming device 10 of thepresent exemplary embodiment as described above, each time a rise orfall is detected in step 210, calculates, in step 215, the totals E1 andE2 of durations (T0 to T3 and T1 to T4) representing detection intervalsof rises and falls detected in the pre-specified first number (T0, T1,T2 and T3 being four and T1, T2, T3 and T4 being four) prior to thecurrent rise or fall detected in step 210. For each of the calculatedtotal durations E1 and E2, control is performed in step 219 to memorizea pre-specified number (two in the present exemplary embodiment) oftotal durations E1 and E2 in the NVM 76 as a history. The duration E isestimated on the basis of, of the pre-specified number of totaldurations E1 and E2 memorized in the NVM 76, the second number (two inthe present exemplary embodiment) of total durations E1 and E2, and theperipheral face speed V of the image forming drum 44 is calculated instep 221 by dividing the movement distance (R₀θ₀) of the peripheral faceof the image forming drum 44 through the rotation angle θ₀ by theestimated duration E.

Here, the pre-specified third number and second number may be numberslarger than two, and the duration E may be estimated by higher orderextrapolation in step 221 on the basis of the second number of totaldurations. Furthermore, the pre-specified third number and second numberneed not be the same number. It is sufficient that the pre-specifiedthird number be at least as large as the second number.

Third Exemplary Embodiment

Next, a third exemplary embodiment will be described. Portions of thepresent exemplary embodiment that are the same as in the first exemplaryembodiment are assigned the same reference numerals and will not bedescribed.

In the first exemplary embodiment, an example is described in which theprograms for executing the image formation control processing shown inFIG. 5 and the speed calculation processing shown in FIG. 6 arememorized in the ROM 72, the CPU 70 reads the program from the ROM 72and executes the image formation control processing shown in FIG. 5, andthe FPGA 79 reads the program from the ROM 72 and executes the speedcalculation processing shown in FIG. 6. In the present exemplaryembodiment, programs for executing the image formation controlprocessing shown in FIG. 13 and the speed calculation processing shownin FIG. 14 are memorized in the ROM 72 in advance, the CPU 70 reads theprogram from the ROM 72 and executes the image formation controlprocessing shown in FIG. 13, and the FPGA 79 reads the program from theROM 72 and executes the speed calculation processing shown in FIG. 14.

Now the image formation control processing that is executed by the CPU70 of the present exemplary embodiment will be described referring toFIG. 13.

Firstly, the same as in the first exemplary embodiment, in step 100, aninstruction to commence execution of the speed calculation processing isoutputted to the FPGA 79, and the FPGA 79 performs control so as tocommence execution of the speed calculation processing.

Now the speed calculation processing that is executed by the FPGA 79 ofthe present exemplary embodiment will be described referring to FIG. 14.

Firstly, in step 201, the rotation angle θ₀ is read from the ROM 72.Then the processing advances to step 202.

Steps 202, 204, 206, 208, 210, 212, 214 and 216 (steps 202 to 216) arethe same as in the first exemplary embodiment, so will not be described.In step 216 in the present exemplary embodiment, by judging whether ornot all the values of variable T0, variable T1, variable T2 and variableT3 are greater than zero, it is determined (when the judgement ispositive) when information that will be required when calculating aspeed in step 230, details of which are described below, is all present,after which the processing advances to step 230.

In step 230, a speed relating to rotation of the image forming drum 44is calculated on the basis of the duration E1 calculated in theearlier-described step 214 and the rotation angle θ₀ of the imageforming drum 44 that corresponds to one pulse of the pulse signal. Morespecifically, in step 230, an angular speed W of the image forming drum44 is calculated by dividing the rotation angle θ₀ by the duration E1,as in the following equation (8).W=θ ₀ /E1  Equation (8)

Then, in step 232, the value of the angular speed W calculated in step230 is outputted (reported) to the CPU 70. Then the processing advancesto step 222.

Now the description of the image formation control processing shown inFIG. 13 is resumed. In the next step 103, it is determined whether ornot a value of the angular speed W has been received from the FPGA 79.The determination processing of step 103 is repeated until reception isdetermined. When reception is determined in step 103, the processingadvances to the next step 105.

Then, in step 105, the distance R₀ and the distance X₀ are read from theROM 72, and the angular speed W calculated in the above speedcalculation processing is used to calculate, with the following equation(9), a period P of the clock signal that prescribes timings of ejectionsof ink droplets from the nozzles 48 a.

$\begin{matrix}{P = {{{X_{0}/R_{0}}W}\mspace{14mu} = {X_{0}E\;{1/\left( {R_{0}\theta_{0}} \right)}}}} & {{Equation}\mspace{14mu}(9)}\end{matrix}$

Then the processing advances to step 106, and subsequent processing thesame as in the first exemplary embodiment is performed, except that theprocessing returns to step 103 when the determination of step 108 isnegative in the present exemplary embodiment.

The speed calculation device of the image forming device 10 of thepresent exemplary embodiment as described above is constituted toinclude the rotary encoder 52 to serve as the generation component thatgenerates plural pulse signals with different phases (in the presentexemplary embodiment, the pulse signals with phase A and phase B) inaccordance with rotation of the image forming drum 44 which serves asthe rotating body that rotates. The speed calculation device of theimage forming device 10 of the present exemplary embodiment detectsrises and falls of respective pulses of the plural pulse signalsgenerated by the rotary encoder 52 in step 210. Then the speedcalculation device of the image forming device 10 of the presentexemplary embodiment, each time a rise or fall is detected in step 210,calculates, in step 214, the total duration E1 of durations (T0, T1, T2and T3) representing detection intervals of the rises and falls detectedin the pre-specified number (T0, T1, T2 and T3 being four) prior to thecurrent rise or fall detected in step 210. Hence, the speed calculationdevice of the image forming device 10 of the present exemplaryembodiment calculates a speed relating to rotation of the image formingdrum 44 in step 230 on the basis of the total duration E1 and therotation angle θ₀ of the image forming drum 44 corresponding to onepulse of the pulse signal generated by the rotary encoder 52. Morespecifically, the angular speed W of the image forming drum 44 iscalculated in step 230 by dividing the rotation angle θ₀ of the imageforming drum 44 that corresponds to one pulse of the pulse signals bythe total duration E1. Further, the image forming device 10 of thepresent exemplary embodiment is constituted to include inkjet recordingheads 48 in which the nozzles 48 a that serve as plural image formingelements, which form dots that respectively constitute an image at apredetermined surface synchronously with a clock signal, are arranged.The image forming drum 44 rotates with the peripheral face thereofopposing the plural nozzles 48 a in the state in which the recordingpaper W, which serves as the recording medium, is retained at theperipheral face of the image forming drum 44, such that the image isformed at the recording paper W by the respective plural nozzles 48 a.The image forming device 10 of the present exemplary embodimentcalculates a period P of the clock signal in step 105 on the basis ofthe angular speed W calculated by the speed calculation device, thedistance R₀ between the axis of the image forming drum 44 and theperipheral face of the image forming drum 44, and the distance X₀between neighboring dots.

Fourth Exemplary Embodiment

Next, a fourth exemplary embodiment will be described. Portions of thepresent exemplary embodiment that are the same as in the first exemplaryembodiment, the second exemplary embodiment and the third exemplaryembodiment are assigned the same reference numerals and will not bedescribed.

In the present exemplary embodiment, programs for executing the imageformation control processing shown in FIG. 13 and the speed calculationprocessing shown in FIG. 15 are memorized in the ROM 72 in advance, theCPU 70 reads the program from the ROM 72 and executes the imageformation control processing shown in FIG. 13, and the FPGA 79 reads theprogram from the ROM 72 and executes the speed calculation processingshown in FIG. 15.

Now the speed calculation processing that is executed by the FPGA 79 ofthe present exemplary embodiment will be described referring to FIG. 15.

Firstly, in step 201, the same as in the third exemplary embodiment, therotation angle θ₀ is read from the ROM 72. Then the processing advancesto step 202.

Steps 202, 204, 207, 208, 210, 212, 215, 217 and 219 (steps 202 to 219)are the same as in the second exemplary embodiment, so will not bedescribed. In the present exemplary embodiment, after step 219 theprocessing advances to step 240.

In step 240, a speed relating to rotation of the image forming drum 44is calculated on the basis of the pre-specified second number of totaldurations E1 and E2 (E1 and E2 being two in the present exemplaryembodiment) and the rotation angle θ₀ of the image forming drum 44 thatcorresponds to one pulse of the pulse signal. More specifically, in step240 a duration E, for calculating the speed relating to rotation of theimage forming drum 44 (the angular speed W in the present exemplaryembodiment) that is to be calculated a next time, is estimated by linearextrapolation similarly to the second exemplary embodiment, based on, ofthe total durations E1 and E2 memorized in the NVM 76, the pre-specifiedsecond number of total durations E1 and E2 (E1 and E2 being two in thepresent exemplary embodiment), and the angular speed W of the imageforming drum 44 is calculated by dividing the rotation angle θ₀ by theestimated duration E, as in the following equation (10).

$\begin{matrix}{W = {{\theta_{0}/E}\mspace{25mu} = {{\theta_{0}/\left( {{3.5*E\; 2} - {2.5*E\; 1}} \right)}\mspace{25mu} = {2\;{\theta_{0}/\left( {{7*E\; 2} - {5*E\; 1}} \right)}}}}} & {{Equation}\mspace{14mu}(10)}\end{matrix}$

Then the processing advances to step 242. In step 242, the value of theangular speed W calculated in step 240 is outputted (reported) to theCPU 70. Then the processing advances to step 222 and subsequentprocessing the same as in the third exemplary embodiment is performed.

In the above description, a speed at an intermediate point during t₆-t₇is estimated. However, a speed at t₆ may be estimated to serve as therepresentative speed W. The angular speed W calculated in step 240 inthis case is represented by the following equation (11).W=θ ₀/(3*E2−2*E1)  Equation (11)

Similarly, a speed at t₇ may be estimated to serve as the representativespeed W. The angular speed W that is calculated in step 240 in this caseis represented by the following equation (12).W=θ ₀/(4*E2−3*E1)  Equation (12)

The speed calculation device of the image forming device 10 of thepresent exemplary embodiment as described above, each time a rise orfall is detected in step 210, calculates, in step 215, the durations ofthe totals E1 and E2 of durations (T0 to T3 and T1 to T4) representingdetection intervals of rises and falls detected in the pre-specifiedfirst number (T0, T1, T2 and T3 being four and T1, T2, T3 and T4 beingfour) prior to the current rise or fall detected in step 210. For eachof the calculated total durations E1 and E2, control is performed instep 219 to memorize a pre-specified number (two in the presentexemplary embodiment) of the total durations E1 and E2 in the NVM 76 asa history. The duration E is estimated on the basis of, of thepre-specified number of total durations E1 and E2 memorized in the NVM76, the second number (two in the present exemplary embodiment) of totaldurations E1 and E2, and the angular speed W of the image forming drum44 is calculated in step 240 by dividing the rotation angle θ₀ by theestimated duration E.

Fifth Exemplary Embodiment

Next, a fifth exemplary embodiment will be described. Portions of thepresent exemplary embodiment that are the same as in the first exemplaryembodiment, the second exemplary embodiment, the third exemplaryembodiment and the fourth exemplary embodiment are assigned the samereference numerals and will not be described.

In the present exemplary embodiment, programs for executing the imageformation control processing shown in FIG. 5 and the speed calculationprocessing shown in FIG. 16 are memorized in the ROM 72 in advance, theCPU 70 reads the program from the ROM 72 and executes the imageformation control processing shown in FIG. 5, and the FPGA 79 reads theprogram from the ROM 72 and executes the speed calculation processingshown in FIG. 16.

Now the speed calculation processing that is executed by the FPGA 79 ofthe present exemplary embodiment will be described referring to FIG. 16.

Steps 200, 202 and 204 (steps 200 to 204) are the same as in the firstexemplary embodiment, so will not be described. In the present exemplaryembodiment, after step 204 the processing advances to step 250.

In step 250, variables—a variable i, a variable T0, a variable T1, avariable T2, a variable T3, a variable E1, a variable V1 and a variableV2—are initialized by setting values of the variables to zero. Then theprocessing advances to step 208. Hence, steps 208, 210, 212, 214 and 216(steps 208 to 216) are the same as in the first exemplary embodiment, sowill not be described. In the present exemplary embodiment, when thedetermination of step 216 is positive, the processing advances to step252.

In step 252, a speed V_(k) relating to rotation of the image formingdrum 44 is detected on the basis of the total duration E1 and therotation angle θ₀ of the image forming drum 44 that corresponds to onepulse of the pulse signals. More specifically, in step 252, theperipheral face speed V_(k) of the image forming drum 44 is detected bydividing the movement distance (R₀θ₀) of the peripheral face of theimage forming drum 44 through the rotation angle θ₀ by the totalduration E1, as in the following equation (13).V _(k)=(R ₀θ₀)/E1  Equation (13)

Herein, step 252 corresponds to a speed detection section of a speedcalculation component.

Then, in step 254, the value of variable V1 is updated by putting thevalue of variable V2 into variable V1, and the value of variable V2 isupdated by putting the value of variable V_(k) into variable V2.

Next, in step 256, by judging whether or not all the values of variableV1 and variable V2 are greater than zero, it is determined whether ornot information that will be required when calculating a speed in step258, details of which are described below, is all present.

In step 256, if it is judged that there is a variable among all thevariables of variable V1 and variable V2 whose value is zero, it isdetermined that not all the information that would be required whencalculating the speed in step 258 whose details are described below ispresent, and the processing returns to step 208. On the other hand, ifit is judged in step 256 that the values of all the variables ofvariable V1 and variable V2 are greater than zero, it is determined thatall the information that will be required when calculating the speed instep 258 whose details are described below is present, and theprocessing advances to the next step 258.

In step 258, a speed relating to rotation of the image forming drum 44that is to be detected subsequent to the speed relating to rotation ofthe image forming drum 44 that has been currently detected in step 252is calculated by estimation, by linear extrapolation on the basis of thepre-specified second number (V1 and V2 being two in the presentexemplary embodiment) of speeds relating to rotation of the imageforming drum 44 (peripheral face speeds in the present exemplaryembodiment), as in the following equation (14). More specifically, instep 258, a peripheral face speed V of the image forming drum 44 to bedetected subsequent to the peripheral face speed V_(k) of the imageforming drum 44 that has been detected in step 252 at the current timeis calculated by estimation, on the basis of the pre-specified secondnumber of peripheral face speeds V1 and V2, as in the following equation(14).V=3*V2−2*V1  Equation (14)

In step 258, the peripheral face speed V may be estimated as in thefollowing equation (15).V=4*V2−3*V1  Equation (15)

Herein, steps 254, 256 and 258 (steps 254 to 258) correspond to thespeed detection section of the speed calculation component.

Then, in step 260, the value of the peripheral face speed V calculatedin step 258 is outputted (reported) to the CPU 70. Then the processingadvances to step 222.

The speed calculation device of the image forming device 10 of thepresent exemplary embodiment as described above, each time a rise orfall is detected in step 210, calculates, in step 214, the duration ofthe total E1 of the durations (T0 to T3 and T1 to T4) representingdetection intervals of rises and falls that have been detected in thepre-specified first number (T0, T1, T2 and T3 being four and T1, T2, T3and T4 being four) prior to the current rise or fall detected in step210. A speed relating to rotation of the image forming drum 44 (theperipheral face speed in the present exemplary embodiment) is detectedin step 252 on the basis of the calculated total duration E1 and therotation angle θ₀, and after the pre-specified number (V1 and V2 beingtwo in the present exemplary embodiment) of speeds relating to rotationof the image forming drum 44 have been detected in step 252 (i.e., whenthe determination in step 256 is positive), a speed relating to rotationof the image forming drum 44 that will be detected in step 252 iscalculated by estimation in step 258.

Sixth Exemplary Embodiment

Next, a sixth exemplary embodiment will be described. Portions of thepresent exemplary embodiment that are the same as in the first exemplaryembodiment, the second exemplary embodiment, the third exemplaryembodiment, the fourth exemplary embodiment and the fifth exemplaryembodiment are assigned the same reference numerals and will not bedescribed.

In the present exemplary embodiment, programs for executing the imageformation control processing shown in FIG. 13 and the speed calculationprocessing shown in FIG. 17 are memorized in the ROM 72 in advance, theCPU 70 reads the program from the ROM 72 and executes the imageformation control processing shown in FIG. 13, and the FPGA 79 reads theprogram from the ROM 72 and executes the speed calculation processingshown in FIG. 17.

Now the speed calculation processing that is executed by the FPGA 79 ofthe present exemplary embodiment will be described referring to FIG. 17.

Steps 201, 202 and 204 (steps 201 to 204) are the same as in the thirdexemplary embodiment, so will not be described. In the present exemplaryembodiment, after step 204 the processing advances to step 261.

In step 261, variables—a variable i, a variable T0, a variable T1, avariable T2, a variable T3, a variable E1, a variable W1 and a variableW2—are initialized by setting values of the variables to zero. Then theprocessing advances to step 208. Hence, steps 208, 210, 212, 214 and 216(steps 208 to 216) are the same as in the first exemplary embodiment (orthe third exemplary embodiment), so will not be described. In thepresent exemplary embodiment, when the determination of step 216 ispositive, the processing advances to step 262.

In step 262, a speed W_(k) relating to rotation of the image formingdrum 44 is detected on the basis of the total duration E1 and therotation angle θ₀ of the image forming drum 44 that corresponds to onepulse of the pulse signals. More specifically, in step 262, the speedW_(k) of the rotation of the image forming drum 44 is detected bydividing the rotation angle θ₀ by the total duration E1, as in thefollowing equation (16).W _(k)=θ₀ /E1  Equation (16)

Herein, step 262 corresponds to the speed detection section of the speedcalculation component.

Then, in step 264, the value of variable W1 is updated by putting thevalue of variable W2 into variable W1, and the value of variable W2 isupdated by putting the value of variable W_(k) into variable W2.

Next, in step 266, by judging whether or not all the values of variableW1 and variable W2 are greater than zero, it is determined whether ornot information that will be required when calculating a speed in step268, details of which are described below, is all present.

In step 266, if it is judged that there is a variable among all thevariables of variable W1 and variable W2 whose value is zero, it isdetermined that not all the information that would be required whencalculating the speed in step 268 whose details are described below ispresent, and the processing returns to step 208. On the other hand, ifit is judged in step 266 that the values of all the variables ofvariable W1 and variable W2 are greater than zero, it is determined thatall the information that will be required when calculating the speed instep 268 whose details are described below is present, and theprocessing advances to the next step 268.

In step 268, a speed relating to rotation of the image forming drum 44that is to be detected subsequent to the speed W_(k) relating torotation of the image forming drum 44 that has been currently detectedin step 262 is calculated by estimation, by linear extrapolation on thebasis of the pre-specified second number (W1 and W2 being two in thepresent exemplary embodiment) of speeds relating to rotation of theimage forming drum 44 (angular speeds in the present exemplaryembodiment), as in the following equation (17). More specifically, instep 268, an angular speed W of the image forming drum 44 to be detectedsubsequent to the angular speed W_(k) that has been detected in step 262at the current time is calculated by estimation, on the basis of thepre-specified second number of angular speeds W1 and W2, as in thefollowing equation (17).W=3*W2−2*W1  Equation (17)

In step 268, the angular speed W may be estimated as in the followingequation (18).W=4*W2−3*W1  Equation (18)

Steps 264, 266 and 268 (steps 264 to 268) correspond to the speeddetection section of the speed calculation component.

Then, in step 270, the value of the angular speed W calculated in step268 is outputted (reported) to the CPU 70. Then the processing advancesto step 222.

The speed calculation device of the image forming device 10 of thepresent exemplary embodiment as described above, each time a rise orfall is detected in step 210, calculates, in step 214, the duration ofthe total E1 of the durations (T0 to T3 and T1 to T4) representingdetection intervals of rises and falls that have been detected in thepre-specified first number (T0, T1, T2 and T3 being four and T1, T2, T3and T4 being four) prior to the current rise or fall detected in step210. A speed relating to rotation of the image forming drum 44 (theangular speed W_(k) in the present exemplary embodiment) is detected instep 262 on the basis of the calculated total duration E1 and therotation angle θ₀, and after the pre-specified number (W1 and W2 beingtwo in the present exemplary embodiment) of speeds relating to rotationof the image forming drum 44 have been detected in step 262 (i.e., whenthe determination in step 266 is positive), a speed relating to rotationof the image forming drum 44 that will be detected in step 262 iscalculated by estimation in step 268.

In the exemplary embodiments described above (the first exemplaryembodiment, the second exemplary embodiment, the third exemplaryembodiment, the fourth exemplary embodiment, the fifth exemplaryembodiment and the sixth exemplary embodiment), examples are describedin which the present invention is applied to calculating a speed (theperipheral face speed V or the angular speed W) relating to rotation ofthe image forming drum 44 which serves as the rotating body in the imageforming device 10 with the structure illustrated in FIG. 1. However, thepresent invention is not to be limited thus. For example, the presentinvention may be applied when calculating speeds of rotating bodies. Forexample, the present invention may be applied to a case of detecting aconveyance speed of a conveyance belt 328, by calculating a speed (aperipheral face speed or an angular speed) of a driving roller 324 whichserves as a rotating body in an image forming device 312 as illustratedin FIG. 18, and altering a period P of a clock signal in accordance withthe conveyance speed, or the like.

Now, general structure of the image forming device 312 illustrated inFIG. 18 will be described. As is shown in FIG. 18, a paper supply tray316 is provided at a lower portion of the interior of a casing 314 ofthe image forming device 312, and recording paper W that is stacked inthe paper supply tray 316 may be taken out one sheet at a time by apickup roller 318. The recording paper W that is taken out is conveyedby plural conveyance roller pairs 320 which constitute a predeterminedconveyance path 322. Herebelow, where simply “the conveyance direction”is referred to, this means a conveyance direction of the recording paperW, and where “upstream” and “downstream” are referred to, these meanupstream and downstream, respectively, in the conveyance direction.

The conveyance belt 328 is provided above the paper supply tray 316 inan endless form spanning between the driving roller 324 and a drivenroller 326. The driving roller 324 receives driving force from the motor30 and rotates. The driving roller 324 is equipped with the rotaryencoder 52.

A recording head array 330 is disposed above the conveyance belt 328,opposing a flat portion 328F of the conveyance belt 328. This opposingregion is an ejection region SE at which ink drops are ejected from therecording head array 330. The recording paper W that has been conveyedalong the conveyance path 322 is retained at the conveyance belt 328 andreaches the ejection region SE, and in a state in which the recordingpaper W opposes the recording head array 330, ink droplets from therecording head array 330 are applied thereto in accordance with imageinformation.

Then, by the recording paper W being conveyed in the state of beingretained at the conveyance belt 328, the recording paper W passesthrough the interior of the ejection region SE and image formation maybe performed. The recording paper W may be passed through the interiorof the ejection region SE a plural number of times by being circulatedin the state in which the recording paper W is retained at theconveyance belt 328. Thus, image formation with “multipassing” may beperformed.

At the recording head array 330, four inkjet recording heads 332,corresponding to four respective colors Y, M, C and K, are arrangedalong the conveyance direction, effective recording regions thereofhaving long strip forms of at least the width of the recording paper W(i.e., the length in a direction orthogonal to the conveyancedirection). Thus, full-color images may be formed. The inkjet recordingheads 332 have the same constitution as the inkjet recording heads 48described in the first exemplary embodiment, and similarly to the inkjetrecording heads 48, include the nozzles 48 a. Operations of the inkjetrecording heads 332 are controlled by the recording head controller 84described in the first exemplary embodiment.

A charging roller 335, to which a power supply is connected, is disposedat the upstream side of the recording head array 330. The chargingroller 335 nips and is driven by the conveyance belt 328 and therecording paper W between the charging roller 335 and the driving roller324, and is formed to be movable between a pressing position, whichpresses the recording paper W against the conveyance belt 328, and awithdrawn position, which is withdrawn from the conveyance belt 328.When at the pressing position, the charging roller 335 provideselectronic charge to the recording paper W and causes the recordingpaper W to be electrostatically adhered to the conveyance belt 328.

A separation plate 340, which is formed with an aluminium plate or thelike, is disposed at the downstream side of the recording head array330. The separation plate 340 is capable of separating the recordingpaper W from the conveyance belt 328. The separated recording paper W isconveyed by plural ejection roller pairs 342, which constitute anejection path 344 at the downstream side of the separation plate 340,and is ejected to an ejection tray 346 disposed at an upper portion ofthe casing 314.

A cleaning roller 348, which is capable of nipping the conveyance belt328 against the driven roller 326, is disposed below the separationplate 340. The surface of the conveyance belt 328 is cleaned by thecleaning roller 348.

An inversion path 352, which is constituted by plural inversion rollerpairs 350, is provided between the paper supply tray 316 and theconveyance belt 328. The inversion path 352 inverts recording paper W atone face of which image formation has been performed, and causes therecording paper W to be retained at the conveyance belt 328. Thus, imageformation on both faces of the recording paper W is implemented withease.

Ink tanks 354, which respectively store inks of the four colors, aredisposed between the conveyance belt 328 and the ejection tray 346. Theinks in the ink tanks 354 are supplied to the recording head array 330by ink supply piping. Thus, structure of the image forming device 312has been described with reference to FIG. 18.

Furthermore, in the exemplary embodiments described above, examples havebeen described which employ the rotary encoder 52 that generates twopulse signals with phase A and phase B. However, an encoder may beemployed that generates more numerous pulse signals in order to improvethe measurement frequency. For example, an encoder 55 illustrated inFIG. 19 may be employed, which is equipped with eight detectors around acode wheel. If this encoder 55 is employed, tracking of variations inspeed is further improved and clock signals for printing (imageformation) are generated with higher accuracy.

Further, in the exemplary embodiments described above, the inkjetrecording heads 48 or 332 are constituted with the plural nozzles 48 abeing lined up in two rows with respect to the sub-scanning direction.However, the present invention is not to be limited thus. Theconstitutions of the inkjet recording heads 48 or 332 may be anyconstitution as long as the plural nozzles 48 a are two-dimensionallyarranged without overlapping in the sub-scanning direction.

Further, the exemplary embodiments described above have been describedgiving examples of image forming devices of modes which form imagesdirectly on recording paper W with the inkjet recording heads. However,the present invention is not to be limited thus. Image forming devicesof modes that form images on recording paper W via intermediate transferbodies are also possible. Such cases may be exemplified by an imageforming device of a mode in which a latent image is formed on aperipheral face (a predetermined face) of a photosensitive drum, whichis a rotating body, by recording heads that are provided withlight-emitting elements such as LEDs or the like, the latent image isconverted to a toner image, and the toner image is transferred onto asurface of a recording paper.

In addition, the structures of the image forming devices 10 and 312described in the above exemplary embodiments are examples, and may bemodified in accordance with circumstances within a technical scope notdeparting from the spirit of the present invention.

Further, the mathematical formulae described in the above exemplaryembodiments are examples. Unnecessary parameters may be removed and newparameters may be added.

Further, the various processing programs described in the aboveexemplary embodiments are examples. Within a technical scope notdeparting from the spirit of the present invention, unnecessary stepsmay be removed, new steps may be added, and processing sequences may berearranged.

Seventh Exemplary Embodiment

FIG. 1 is a structural diagram illustrating structure of a rotaryencoder relating to a seventh exemplary embodiment. As shown in FIG. 1,the paper supply conveyance section 12 that supplies and conveysrecording paper W, which is a recording medium, is provided at the imageforming device 10. At the conveyance direction downstream side of thepaper supply conveyance section 12, the processing fluid applicationsection 14, the image formation section 16, the drying section 18, theimage fixing section 20 and the ejection conveyance section 24 areprovided along the conveyance direction of the recording paper W. Theprocessing fluid application section 14 applies the processing fluid tothe recording face (front face) of the recording paper W. The imageformation section 16 forms an image on the recording face of therecording paper W. The drying section 18 dries the image that has beenformed at the recording face. The image fixing section 20 fixes thedried image to the recording paper W. The ejection conveyance section 24conveys the recording paper W to which the image has been fixed to theejection section 22.

The paper supply conveyance section 12 is provided with theaccommodation section 26 that accommodates the recording paper W, andthe motor 30 is provided at the accommodation section 26. The papersupply apparatus is also provided at the accommodation section 26, andthe recording paper W is fed out from the accommodation section 26toward the processing fluid application section 14 by the paper supplyapparatus.

The processing fluid application section 14 is provided with theintermediate conveyance drum 28A and the processing fluid applicationdrum 36. The intermediate conveyance drum 28A is rotatably disposed in aregion sandwiched between the accommodation section 26 and theprocessing fluid application drum 36. The belt 32 spans between therotation axle of the intermediate conveyance drum 28A and the rotationaxle of the motor 30. Accordingly, rotary driving force of the motor 30is transmitted to the intermediate conveyance drum 28A via the belt 32,and the intermediate conveyance drum 28A rotates in the direction ofarrow A.

The retention member 34 that nips a distal end portion of the recordingpaper W and retains the recording paper W is provided at theintermediate conveyance drum 28A. The recording paper W that is fed outfrom the accommodation section 26 to the processing fluid applicationsection 14 is retained at the peripheral face of the intermediateconveyance drum 28A by the retention member 34, and is conveyed to theprocessing fluid application drum 36 by the rotation of the intermediateconveyance drum 28A.

Similarly to the intermediate conveyance drum 28A, the retention members34 are provided at the intermediate conveyance drums 28B, 28C, 28D and28E, the processing fluid application drum 36, the image forming drum44, the ink drying drum 56, the image fixing drum 62 and the ejectionconveyance drum 68, which are described below. The recording paper W ispassed along from upstream side drums to downstream side drums by theseretention members 34.

A rotation axle of the processing fluid application drum 36 is linkedwith the rotation axle of the intermediate conveyance drum 28A by gears,and receives rotary force from the intermediate conveyance drum 28A androtates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28A is taken up onto the processing fluid applicationdrum 36 by the retention member 34 of the processing fluid applicationdrum 36, and is conveyed in the state of being retained at the outerperipheral face of the processing fluid application drum 36.

At the upper portion of the processing fluid application drum 36, theprocessing fluid application roller 38 is disposed in the state oftouching against the outer peripheral face of the processing fluidapplication drum 36, and the processing fluid is applied to therecording face of the recording paper Won the outer peripheral face ofthe processing fluid application drum 36 by the processing fluidapplication roller 38.

The recording paper W to which the processing fluid has been applied bythe processing fluid application section 14 is conveyed to the imageformation section 16 by the rotation of the processing fluid applicationdrum 36.

The image formation section 16 is provided with the intermediateconveyance drum 28B and the image forming drum 44. The rotation axle ofthe intermediate conveyance drum 28B is linked with the rotation axle ofthe processing fluid application drum 36 by gears, and receives rotaryforce from the processing fluid application drum 36 and rotates.

The recording paper W that has been conveyed by the processing fluidapplication drum 36 is taken up onto the intermediate conveyance drum28B by the retention member 34 of the intermediate conveyance drum 28Bof the image formation section 16, and is conveyed in the state of beingretained at the outer peripheral face of the intermediate conveyancedrum 28B.

The rotation axle of the image forming drum 44, which serves as an imageconveyance component, is linked with the rotation axle of theintermediate conveyance drum 28B by gears, and receives rotary forcefrom the intermediate conveyance drum 28B and rotates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28B is taken up onto the image forming drum 44 by theretention member 34 of the image forming drum 44, and is conveyed in thestate of being retained at the outer peripheral face of the imageforming drum 44.

Above the image forming drum 44, the head unit 46 is disposed close tothe outer peripheral face of the image forming drum 44. The head unit 46is provided with the four inkjet recording heads 48, corresponding toeach of the four colors yellow (Y), magenta (M), cyan (C) and black (K).These inkjet recording heads 48 are arranged along the peripheraldirection of the image forming drum 44, and form an image by ejectingink droplets from the nozzles 48 a, which will be described later,synchronously with clock signals, which will be described later, suchthat the ink droplets are superposed with the layer of processing fluidthat has been formed on the recording face of the recording paper W bythe processing fluid application section 14.

The image forming drum 44 is provided with the rotary encoder 52, whichwill be described in more detail later. The rotary encoder 52, inaccordance with the rotation of the image forming drum 44, generates apulse signal for detecting a pre-specified rotation reference positionof the image forming drum 44 and plural pulse signals with phasedifferences, which are pulse signals for detecting rotation angles fromthe pre-specified rotation reference position of the image forming drum44.

As illustrated by the example in FIG. 20, the rotary encoder 52 relatingto the present seventh exemplary embodiment is structured to include acircular plate-form code wheel 53, which serves as a rotating body, anda pulse signal generation section 55, which serves as a generationcomponent. The code wheel 53 is fixed to the image forming drum 44 suchthat a central portion thereof is disposed at a central portion of theimage forming drum 44. Plural slits 53A, which serve as detectedportions, are formed in the code wheel 53, extending outward in radialdirections from the central portion and arranged at equidistantintervals along the circumferential direction. The pulse signalgeneration section 55 senses the slits 53A and generates the pluralpulse signals with phase differences. The pulse signal generationsection 55 relating to the seventh exemplary embodiment is constitutedwith an A-phase transmission-type photosensor and a B-phasetransmission-type photosensor. The A-phase transmission-type photosensoris structured with a light emission element and a light detectionelement that are disposed so as to face one another sandwiching the codewheel 53, detects the slits 53A and generates an A-phase pulse signal.The B-phase transmission-type photosensor is structured with a lightemission element and a light detection element that are disposed so asto face one another sandwiching the code wheel 53, detects the slits 53Aand generates a B-phase pulse signal.

In the seventh exemplary embodiment, the spacing between adjacent slits53A formed in the code wheel 53 corresponds to a reference rotationangle θ₀ of the code wheel 53 (for example, 1.257 milliradians).

In the code wheel 53, a reference slit is provided closer to the centralportion than the plural slits 53A. The reference slit is for detecting arotation reference position of the code wheel 53 that corresponds to thepre-specified rotation reference position of the image forming drum 44.A transmission-type photosensor is provided at a housing of the imageforming device 10, separately from the transmission-type photosensorsthat constitutes the pulse signal generation section 55, for detectingthe reference slit.

The recording paper W on which the image has been formed at therecording face by the image formation section 16 is conveyed to thedrying section 18 by the rotation of the image forming drum 44.

The drying section 18 is provided with the intermediate conveyance drum28C and the ink drying drum 56. The rotation axle of the intermediateconveyance drum 28C is linked with the rotation axle of the imageforming drum 44 by gears, and receives rotary force from the imageforming drum 44 and rotates.

The recording paper W that has been conveyed by the image forming drum44 is taken up onto the intermediate conveyance drum 28C by theretention member 34 of the intermediate conveyance drum 28C, and isconveyed in the state of being retained at the outer peripheral face ofthe intermediate conveyance drum 28C.

The rotation axle of the ink drying drum 56 is linked with the rotationaxle of the intermediate conveyance drum 28C by gears, and receivesrotary force from the intermediate conveyance drum 28C and rotates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28C is taken up onto the ink drying drum 56 by theretention member 34 of the ink drying drum 56, and is conveyed in thestate of being retained at the outer peripheral face of the ink dryingdrum 56.

Above the ink drying drum 56, the hot air heater 58 is disposed close tothe outer peripheral face of the ink drying drum 56. Excess solvent inthe image that has been formed on the recording paper W is removed byhot air from the hot air heater 58. The recording paper W at which theimage on the recording face has been dried by the drying section 18 isconveyed to the image fixing section 20 by the rotation of the inkdrying drum 56.

The image fixing section 20 is provided with the intermediate conveyancedrum 28D and the image fixing drum 62. The rotation axle of theintermediate conveyance drum 28D is linked with the rotation axle of theink drying drum 56 by gears, and receives rotary force from the inkdrying drum 56 and rotates.

The recording paper W that has been conveyed by the ink drying drum 56is taken up onto the intermediate conveyance drum 28D by the retentionmember 34 of the intermediate conveyance drum 28D, and is conveyed inthe state of being retained at the outer peripheral face of theintermediate conveyance drum 28D.

The rotation axle of the image fixing drum 62 is linked with therotation axle of the intermediate conveyance drum 28D by gears, andreceives rotary force from the intermediate conveyance drum 28D androtates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28D is taken up onto the image fixing drum 62 by theretention member 34 of the image fixing drum 62, and is conveyed in thestate of being retained at the outer peripheral face of the image fixingdrum 62.

At the upper portion of the image fixing drum 62, the fixing roller 64with the heater thereinside is provided in the state in which pressingagainst or being separated from the outer peripheral face of the imagefixing drum 62 may be selected. The recording paper W retained at theouter peripheral face of the image fixing drum 62 is nipped between theouter peripheral face of the image fixing drum 62 and the outerperipheral face of the fixing roller 64 and is heated by the heater inthe state in which the recording paper W is pressed against the fixingroller 64. Thus, colorant in the image formed at the recording face ofthe recording paper W is fused to the recording paper W, and the imageis fixed to the recording paper W. The recording paper W to which theimage has been fixed by the image fixing section 20 is conveyed to theejection conveyance section 24 by the rotation of the image fixing drum62.

The ejection conveyance section 24 is provided with the intermediateconveyance drum 28E and the ejection conveyance drum 68. The rotationaxle of the intermediate conveyance drum 28E is linked with the rotationaxle of the image fixing drum 62 by gears, and receives rotary forcefrom the image fixing drum 62 and rotates.

The recording paper W that has been conveyed by the image fixing drum 62is taken up onto the intermediate conveyance drum 28E by the retentionmember 34 of the intermediate conveyance drum 28E, and is conveyed inthe state of being retained at the outer peripheral face of theintermediate conveyance drum 28E.

The rotation axle of the ejection conveyance drum 68 is linked with therotation axle of the intermediate conveyance drum 28E by gears, andreceives rotary force from the intermediate conveyance drum 28E androtates.

The recording paper W that has been conveyed by the intermediateconveyance drum 28E is taken up onto the ejection conveyance drum 68 bythe retention member 34 of the ejection conveyance drum 68, and isconveyed toward the ejection section 22 in the state of being retainedat the outer peripheral face of the ejection conveyance drum 68.

FIG. 2 is a front view illustrating structure of an inkjet ejectionaperture face side of each inkjet recording head 48 relating to theseventh exemplary embodiment. As shown in FIG. 2, the nozzles 48 a,which serve as plural image formation elements that respectively ejectink droplets, are formed in the face 90 of the inkjet recording head 48that opposes the outer peripheral face of the image forming drum 44.Each inkjet recording head 48 has the structure in which the pluralnozzles 48 a are arranged two-dimensionally (in a staggered matrixpattern in the seventh exemplary embodiment) without overlapping in thedirection of conveyance of the recording paper W by the image formingdrum 44 (the sub-scanning direction). Thus, an increase in density ofthe effective nozzle spacing (projected nozzle pitch) as projected so asto lie along the head length direction (the direction orthogonal to thedirection of conveyance of the recording paper W by the image formingdrum 44 (which is below referred to simply as the conveyance direction))is achieved.

In the inkjet recording head 48 relating to the seventh exemplaryembodiment, the plural nozzles 48 a are arranged with pre-specifiedspacings and are arrayed in nozzle groups of two rows, nozzle group Adisposed at the conveyance direction upstream side and nozzle group Bdisposed at the conveyance direction downstream side. The nozzles 48 aof nozzle group B are arranged so as to be disposed at spaces betweenthe nozzles 48 a of nozzle group A.

FIG. 3 is a block diagram illustrating principal structures of anelectronic system of the image forming device 10 relating to the seventhexemplary embodiment.

The image forming device 10 is structured to include the CPU (centralprocessing unit) 70, ROM (read-only memory) 72, RAM (random accessmemory) 74, NVM (non-volatile memory) 76, UI (user interface) panel 78,FPGA (field-programmable gate array) 79 and communication I/F(communication interface) 80. In the seventh exemplary embodiment, theapparatus including this computer and the rotary encoder 52 correspondsto a speed estimation device that includes a function of estimating aspeed relating to rotation of the image forming drum 44 serving as therotating body.

The CPU 70 administers operations of the image forming device 10 as awhole. The CPU 70 reads a program from the ROM 72 and executes imageformation control processing.

The ROM 72 serves as a memory component at which are memorizedbeforehand: a program for executing the image formation controlprocessing that controls operations of the image forming device 10,which is described in detail hereafter; the reference rotation angle θ₀;a distance from the axial center of the code wheel 53 (which correspondsto a center of the code wheel 53 in the seventh exemplary embodiment) tothe outer peripheral face of the image forming drum 44 (referred tohereafter in the seventh exemplary embodiment as distance R₀), whichcorresponds to a rotation radius of the image forming drum 44; adistance between adjacent dots (herein, between centers of the dots;referred to hereafter in the present exemplary embodiment as distanceX₀); and various parameters and the like. In the seventh exemplaryembodiment, the radius of the image forming drum 44 is employed as thepre-specified distance R₀, but this is not to be limiting and anothervalue may be employed.

The RAM 74 is used as a work area during execution of various programsand the like. The NVM 76 memorizes various kinds of information thatneed to be retained when the power switch of the device is turned off.

The UI panel 78 is structured by a touch panel display, in which atransmissive touch panel is superposed on a display, or the like. The UIpanel 78 displays various kinds of information at a display screen ofthe display, and inputs required information, instructions and the likein accordance with a user touching the touch panel.

The FPGA 79 reads a program from the ROM 72 and executes the speedestimation processing.

The communication interface 80 is connected with the terminal device 82,which is a personal computer or the like, and receives image informationrepresenting an image to be formed at the recording paper W and variousother kinds of information from the terminal device 82.

The CPU 70, the ROM 72, the RAM 74, the NVM 76, the UI panel 78, theFPGA 79 and the communication interface 80 are connected to one anothervia a system bus. Therefore, the CPU 70 may implement each of access tothe ROM 72, the RAM 74 and the NVM 76, display of various kinds ofinformation at the UI panel 78, acquisition of details of controlinstructions from users from the UI panel 78, reception of various kindsof information from the terminal device 82 via the communicationinterface 80, and control of the FPGA 79.

The image forming device 10 is further provided with the recording headcontroller 84 and the motor controller 86.

The recording head controller 84 controls operations of the inkjetrecording head 48 in accordance with instructions from the CPU 70. Themotor controller 86 controls operations of the motor 30.

The recording head controller 84 and the motor controller 86 are alsoconnected to the above-mentioned system bus. Thus, the CPU 70 maycontrol operations of the recording head controller 84 and the motorcontroller 86.

The above-described rotary encoder 52 is also connected to theaforementioned system bus. Thus, the CPU 70 may receive the plural pulsesignals generated by the rotary encoder 52.

Next, operation of the image forming device 10 relating to the seventhexemplary embodiment will be described.

In the image forming device 10 relating to the seventh exemplaryembodiment, recording paper W is fed out from the accommodation section26 to the intermediate conveyance drum 28A by the paper supplyapparatus, the recording paper W is conveyed via the intermediateconveyance drum 28A, the processing fluid application drum 36 and theintermediate conveyance drum 28B to the image forming drum 44, and isretained at the outer peripheral face of the image forming drum 44.Then, ink droplets are ejected at the recording paper W on the imageforming drum 44 from the nozzles 48 a of the inkjet recording heads 48in accordance with image information. Thus, an image represented by theimage information is formed on the recording paper W.

Now, the conveyance speed of the recording paper W that is retained atthe outer peripheral face of the image forming drum 44 varies as isshown by the example in the graph of FIG. 4 for reasons such as, forexample, variations in meshing and loading of the driving system gearsand variations in speed of the motor itself. The vertical axis of thegraph in FIG. 4 shows the conveyance speed of the recording paper W atthe image forming drum 44, and the horizontal axis shows the rotationangle of the image forming drum 44 from the pre-specified rotationreference position. Impact positions of ink dots that are formed toserve as constitutional units constituting the image, corresponding withthe graph in FIG. 4, are shown by the solid line circles. The brokenline circles show an example of impact positions of the ink dropletsejected from the nozzles 48 a in a case in which the conveyance speed ofthe recording paper W is constant at a speed V.

In conditions in which the conveyance speed of the recording paper W atthe image forming drum 44 varies in this manner, when the ink dropletsare ejected from the nozzles 48 a with the constant periodic spacing,the impact positions of the ink droplets are displaced. In order tosuppress this, the rotary encoder 52 is attached to the image formingdrum 44 and the pulse signals are generated by the rotary encoder 52 inaccordance with conveyance speeds of the recording paper W retained atthe outer peripheral face of the image forming drum 44.

These pulse signals are outputted to the inkjet recording heads 48, inkdroplets are ejected from the nozzles 48 a synchronously with theconveyance speeds of the recording paper W, and the image is formed.

In order to suppress the deformation of images due to speed variations,estimating a conveyance speed of the recording paper W and altering thefrequency of the clock signals in accordance with the conveyance speedmay be considered. In order to estimate the conveyance speed of therecording paper W accurately, it is necessary to improve tracking ofvariations of the rotation speed of the image forming drum 44. Employingan apparatus that generates pulse signals with a higher frequency as therotary encoder 52 may be considered for improving tracking of thevariations in the rotation speed of the image forming drum 44. This isbecause it is thought that if the rotary encoder 52 that generates pulsesignals with a higher frequency is employed, the detection interval ofthe rotation speed of the image forming drum 44 is shorter and thetracking of variations of the rotation speed of the image forming drum44 improves. However, when the frequency is higher, the period of thepulse signals that are outputted from the rotary encoder 52 is shorterand measurement accuracy falls.

Accordingly, in the image forming device 10 relating to the seventhexemplary embodiment, in order to suppress deformation of an image dueto variations in speed, the speed estimation processing is executed inorder to improve tracking of variations in a speed relating to rotationof the image forming drum 44 and to estimate the speed relating torotation of the image forming drum 44 with high accuracy.

Next, referring to FIG. 21, operations of the image forming device 10relating to the seventh exemplary embodiment when the image formationcontrol processing is executed for forming an image at the recordingpaper W will be described. FIG. 21 is a flowchart illustrating the flowof processing of an image formation control processing program that isexecuted by the CPU 70 when an instruction for execution of the imageformation processing, and image information representing an image to beformed on the recording paper W, are inputted from the terminal device82 via the communication I/F 80. In the image forming device 10 relatingto the seventh exemplary embodiment, the image formation controlprocessing program is memorized in advance at the ROM 72, which servesas a storage medium, but this is not to be limiting. Modes may beemployed in which the image formation control processing program isprovided having been saved on a storage medium readable by a computer,such as a CD-ROM (compact disc ROM), a DVD-ROM (digital versatile discROM), a USB (universal serial bus) memory or the like, and modes may beemployed in which the program is distributed through a communicationscomponent, by wire or by wireless.

In step 100A of FIG. 21, an instruction to start execution of the speedestimation processing relating to the seventh exemplary embodiment isoutputted to the FPGA 79. Hence, the FPGA 79 performs control so as tostart execution of the speed estimation processing relating to theseventh exemplary embodiment.

Now the speed estimation processing relating to the seventh exemplaryembodiment that is executed by the FPGA 79 will be described referringto FIG. 22. FIG. 22 is a flowchart illustrating a flow of processing ofa speed estimation processing program that is executed by the FPGA 79when the instruction to start execution of the speed estimationprocessing relating to the seventh exemplary embodiment is inputted. Inthe image forming device 10 relating to the seventh exemplaryembodiment, the speed estimation processing program is memorized inadvance at the ROM 72 serving as a storage medium, but this is not to belimiting. Modes may be employed in which the speed estimation processingprogram is provided having been saved on a storage medium readable by acomputer, such as a CD-ROM, DVD-ROM, USB memory or the like, and modesmay be employed in which the program is distributed through acommunications component, by wire or by wireless.

In step 200A of FIG. 22, the rotation angle θ₀ and the distance R₀ areread out from the ROM 72. Then, in step 202A, a rotation startinstruction signal instructing the commencement of rotary driving of theimage forming drum 44 is outputted to the motor controller 86. The motorcontroller 86 receiving the rotation start instruction signal causes themotor 30 to drive for rotation. Hence, the image forming drum 44receives the rotary driving force from the motor 30 and starts to turnin a pre-specified rotation direction. In association therewith, thecode wheel 53 also starts to turn in the pre-specified rotationdirection.

Next, in step 204A, the processing waits until the image forming drum 44reaches a pre-specified rotation speed (for example, 500 mm/s at theposition separated from the center of the code wheel 53 by the distanceR₀ corresponding to the rotation radius of the image forming drum 44).Here, the judgement in step 204A of whether or not the image formingdrum 44 has reached the pre-specified rotation speed is determined bycounting numbers of pulse signals generated by the rotary encoder 52 perunit time, but is not to be limited thereto. It may also be judgedwhether or not a pre-specified duration—a duration until thepre-specified rotation speed is reached and the rotation speedstabilizes—has passed since the image forming drum 44 started to rotate.

Then, in step 206A, variables—variable i, variable T0, variable T1,variable T2, variable T3 and variable E1—are initialized by settingvalues of the variables to zero.

Next, in step 208A, timing by a timer is started, and a duration thathas been measured at that point in time is put into the variable i. Inthe seventh exemplary embodiment, this timer measures durations in, forexample, unit time intervals (for example, of 10 ns (nanoseconds)). Morespecifically, the duration is computed from a clock count of a counterimplemented at the FPGA 79.

Then, in step 210A, pulse reversals, which is to say pulse rises andfalls, of the respective pulses of the two pulse signals of phase A andphase B outputted from the rotary encoder 52 are detected for.Accordingly, when a pulse of either of the two pulse signals with phaseA and phase B rises, the rise of the pulse of that signal is detected,and when a pulse of either of the two pulse signals with phase A andphase B falls, the fall of the pulse of that signal is detected.Herebelow, pulse rises and pulse falls are collectively referred to aspulse reversals.

Next, in step 212A, it is judged whether or not a pulse reversal hasbeen detected in step 210A. If it is judged in step 212A that a pulsereversal has been detected in step 210A, the processing advances to thenext step 214A. On the other hand, if it is judged in step 212A that nopulse reversal has been detected in step 210A, the processing returns tostep 210A, and respective pulse reversals of the two pulse signals withphase A and phase B outputted from the rotary encoder 52 are againdetected for.

In step 214A, the value of variable T0 is updated by putting the valueof variable T1 into variable T0, the value of variable T1 is updated byputting the value of variable T2 into variable T1, the value of variableT2 is updated by putting the value of variable T3 into variable T2, andthe value of variable T3 is updated by putting the value of variable iinto variable T3. Then the value of variable E1 is updated by puttingthe sum of the value of variable T0, the value of variable T1, the valueof variable T2 and the value of variable T3 (T0+T1+T2+T3) into variableE1. Then, initialization is performed by stopping the timing by thetimer that started in step 208A and setting the value of variable i tozero. Here, if the detection of a pulse reversal in the most recentprocessing of step 210A is a first (initial) detection, the value ofvariable i that has been put into variable T3 in the present step 214Ais the duration from the present speed estimation processing startinguntil a first detection. If the detection of a pulse reversal in themost recent processing of step 210A is a second or subsequent detection,this value of variable i is the duration from the previous detection bythe processing of step 210A to the current detection by the processingof step 210A. That is, in step 214A, each time a pulse reversal isdetected in step 210A, the duration E1 is calculated, which is a totalof durations (T0, T1, T2 and T3) representing detection intervals of apre-specified number of the pulse reversals (T0 to T3 being fourthereof) prior to the current pulse reversal detected in step 210A. Thepre-specified number is a number of pulse reversals of the pulse signalsgenerated by the rotary encoder 52 that corresponds to rotation of theimage forming drum 44 through the reference rotation angle θ₀.

Then, in step 216A, by determining whether or not all the values ofvariable T0, variable T1, variable T2 and variable T3 are greater thanzero, it is determined whether or not information that will be requiredwhen calculating a speed in step 218A, details of which are describedbelow, is all present.

In step 216A, if it is judged that there is a variable among all thevariables of variable T0, variable T1, variable T2 and variable T3 whosevalue is zero, it is determined that all the information that would berequired when calculating the speed in step 218A whose details aredescribed below is not present, and the processing returns to step 208A.On the other hand, if it is judged in step 216A that the values of allthe variables of variable T0, variable T1, variable T2 and variable T3are greater than zero, it is determined that all the information thatwill be required when calculating the speed in step 218A whose detailsare described below is present, and the processing advances to the nextstep 218A.

In step 218A, a speed relating to rotation of the image forming drum 44is estimated by calculation on the basis of the total duration E1calculated in step 214A and the reference rotation angle θ₀. Morespecifically, in step 218A, a linear speed at the position separated bythe distance R₀ in the rotation radial direction of the image formingdrum 44 from the center of the code wheel 53, which is to say an outerperiphery speed V of the image forming drum 44, is estimated by dividinga movement distance (R₀θ₀) of the outer peripheral face of the imageforming drum 44 through the rotation angle θ₀ by the total duration E 1,as in equation (1).

Then, in step 220A, the value of the outer periphery speed V calculatedin step 218A is outputted (reported) to the CPU 70.

Next, in step 222A, it is judged whether or not an instruction to stopexecution of the speed estimation processing has been received from theCPU 70. If it is judged in step 222A that an instruction to stopexecution of the speed estimation processing has not been received, theprocessing returns to step 208A. On the other hand, if it is judged instep 222A that an instruction to stop execution of the speed estimationprocessing has been received, the present speed estimation processingprogram ends.

Now the description of the flowchart shown in FIG. 21 is resumed. In thenext step 102A, it is determined whether or not a value of the outerperiphery speed V has been received from the FPGA 79. The determinationprocessing of step 102A is repeated until reception is determined. Whenreception is determined in step 102A, the processing advances to thenext step 104A.

Then, in step 104A, the distance X₀ is read from the ROM 72, the outerperiphery speed V estimated by the speed estimation processing is usedto calculate, with equation (2), a period P of the clock signal thatprescribes timings of ejections of ink droplets from the nozzles 48 a,and the period of the clock signal is corrected by setting this period Pas a new period of the clock signal to be used when ejecting inkdroplets from the nozzles 48 a.

Then, in step 106A, a clock signal with the period P provided by theabove processing of step 104A is generated and instructions to eject inkdroplets from the nozzles 48 a are outputted to the recording headcontroller 84, synchronously with this clock signal, in accordance withthe inputted image information. Hence, the recording head controller 84controls the inkjet recording heads 48 so as to eject ink droplets fromthe nozzles 48 a in accordance with the inputted image information,synchronously with the clock signal with the period P. Thus, the imagerepresented by the image information is formed at the recording face ofthe recording paper W without being affected by variations in theconveyance speed of the recording paper W.

Next, in step 108A, it is judged whether or not image formation with theinputted image information has ended. If this judgement is negative, theprocessing returns to step 102A. On the other hand, if the judgement instep 108A is positive, the processing advances to the next step 110A. Instep 110A, an instruction to stop execution of the speed estimationprocessing is outputted to the FPGA 79. Then, the present imageformation control processing program ends.

In this seventh exemplary embodiment, a detection component correspondsto the processing of step 210A, a calculation component corresponds tothe processing of step 214A, an estimation component corresponds to theprocessing of step 218A, and a correction component corresponds to theprocessing of step 104A.

Eighth Exemplary Embodiment

Next, an eighth exemplary embodiment will be described. Portions of thiseighth exemplary embodiment that are the same as in the seventhexemplary embodiment are assigned the same reference numerals and willnot be described.

In the seventh exemplary embodiment, an example is described in whichthe speed estimation processing program for executing the processing ofthe flowchart shown in FIG. 22 is memorized in advance in the ROM 72,and the FPGA 79 reads the program from the ROM 72 and executes theprocessing of the flowchart shown in FIG. 22. In the eighth exemplaryembodiment, a speed estimation processing program for executing theprocessing of the flowchart shown in FIG. 23 is memorized in the ROM 72in advance, and the FPGA 79 reads the program from the ROM 72 andexecutes the processing of the flowchart shown in FIG. 23.

Now the speed estimation processing relating to the eighth exemplaryembodiment that is executed by the FPGA 79 of the eighth exemplaryembodiment will be described referring to FIG. 23. FIG. 23 is aflowchart illustrating a flow of processing of a speed estimationprocessing program that is executed by the FPGA 79 when an instructionto start execution of the speed estimation processing relating to theeighth exemplary embodiment is inputted. In the image forming device 10relating to the eighth exemplary embodiment, the speed estimationprocessing program is memorized in advance at the ROM 72 serving as astorage medium, but this is not to be limiting. Modes may be employed inwhich the speed estimation processing program is provided having beensaved on a storage medium readable by a computer, such as a CD-ROM,DVD-ROM, USB memory or the like, and modes may be employed in which theprogram is distributed through a communications component, by wire or bywireless. Steps in FIG. 23 that carry out processing the same as in theflowchart shown in FIG. 22 are assigned the same step numbers as in FIG.22 and descriptions thereof will not be given. The description startsfrom step 204A.

When the judgement in step 204A of FIG. 23 is positive, the processingadvances to step 207A. In step 207A, variables—a variable i, a variableT0, a variable T1, a variable T2, a variable T3, a variable T4, avariable E1 and a variable E2—are initialized by setting the values ofthe variables to zero, and the processing advances to step 208A.

When the judgement in step 212A is positive, the processing advances tostep 215A. In step 215A, the value of variable T0 is updated by puttingthe value of variable T1 into variable T0, the value of variable T1 isupdated by putting the value of variable T2 into variable T1, the valueof variable T2 is updated by putting the value of variable T3 intovariable T2, the value of variable T3 is updated by putting the value ofvariable T4 into variable T3, and the value of variable T4 is updated byputting the value of variable i into variable T4. Then the value ofvariable E1 is updated by putting the sum of the value of variable T0,the value of variable T1, the value of variable T2 and the value ofvariable T3 (T0+T1+T2+T3) into variable E1, and the value of variable E2is updated by putting the sum of the value of variable T1, the value ofvariable T2, the value of variable T3 and the value of variable T4(T1+T2+T3+T4) into variable E2. Then, initialization is performed bystopping the timing by the timer that started in step 208A and settingthe value of variable i to zero. Here, if the detection of a pulsereversal in the most recent processing of step 210A is the first(initial) detection, the value of variable i that has been put intovariable T4 in the present step 215A is the duration from the presentspeed estimation processing starting until a first detection. If thedetection of a pulse reversal in the most recent processing of step 210Ais a second or subsequent detection, this value of variable i is theduration from the previous detection by the processing of step 210A tothe current detection by the processing of step 210A. That is, in step215A, each time a pulse reversal is detected in step 210A, the durationE1 is calculated, which is a total of durations (T0, T1, T2 and T3)representing detection intervals of a pre-specified number of the pulsereversals (T0 to T3 being four thereof) prior to the current pulsereversal detected in step 210A, in addition to which the duration E2 iscalculated, which is a total of durations (T1, T2, T3 and T4)representing detection intervals of the pre-specified number of thepulse reversals (T1 to T4 being four thereof) prior to the current pulsereversal detected in step 210A. The pre-specified number is the numberof pulse reversals of the pulse signals generated by the rotary encoder52 in association with rotation of the image forming drum 44 through thereference rotation angle θ₀.

Then, in step 217A, by determining whether or not all the values ofvariable T0, variable T1, variable T2, variable T3 and variable T4 aregreater than zero, it is determined whether or not information that willbe required when estimating a speed in step 221A, details of which aredescribed below, is all present.

In step 217A, if it is judged that there is a variable among all thevariables of variable T0, variable T1, variable T2, variable T3 andvariable T4 whose value is zero, it is determined that all theinformation that would be required when estimating the speed in step221A whose details are described below is not present, and theprocessing returns to step 208A. On the other hand, if it is judged instep 217A that the values of all the variables of variable T0, variableT1, variable T2, variable T3 and variable T4 are greater than zero, itis determined that all the information that will be required whenestimating the speed in step 221A whose details are described below ispresent, and the processing advances to the next step 219A.

In step 219A, for the respective total durations E1 and E2 that havebeen calculated in step 215A, control is performed so as to memorize apre-specified number (E1 and E2 being two in the eighth exemplaryembodiment) of the total durations E1 and E2 in the NVM 76, which servesas a memory component, to serve as a history. Accordingly, the totaldurations E1 and E2 are memorized in the NVM 76.

Then, in step 221A, a speed relating to rotation of the image formingdrum 44 is calculated on the basis of, of the pre-specified number oftotal durations E1 and E2 memorized in the NVM 76, the pre-specifiednumber of total durations E1 and E2 and the reference rotation angle θ₀.More specifically, in step 221A a duration E, for estimating the speedrelating to rotation of the image forming drum 44 (the outer peripheryspeed V in the eighth exemplary embodiment) that is to be estimated anext time, is estimated by linear extrapolation based on, of thepre-specified number of total durations E1 and E2 memorized in the NVM76, the pre-specified number of total durations E1 and E2 (E1 and E2being two in the eighth exemplary embodiment), and the outer peripheryspeed V of the image forming drum 44 is estimated by dividing themovement distance (R₀θ₀) of the outer peripheral face of the imageforming drum 44 through the reference rotation angle θ₀ by the durationE, as in equation (3). Then the processing advances to step 220A.

Now, the processing of step 221A will be more specifically describedwith reference to FIG. 11.

As shown in FIG. 11, the period (total duration) represented by the mostrecent pulse signals from the rotary encoder 52 is E2, and the period(total duration) one step prior thereto is E1. The speed V1 (=(R₀θ₀)/E1)calculated with E1 is the average speed over t₁-t₅, and the speed V2(=(R₀θ₀)/E2) calculated with E2 is the average speed over t₂-t₆. Theduration E1 and the duration E2 correspond with the times t₃ and t₄,respectively, and the speed V1 and the speed V2 correspond to speeds atthe times t₃ and t₄, respectively.

Given that the intervals t_(i) to t_(i+1) are substantially equalintervals, if the period at an intermediate point between t₆ and t₇ isthe duration E, duration E is expressed by equation (20), derived fromthe following equation (19) by linear extrapolation. The speed to beestimated from E1 and E2 is the speed V at the intermediate pointbetween t₆ and t₇. The speed V at the intermediate point between t₆ andt₇ is represented by equation (4), derived from equation (3) andequation (20).7:2=(E−E1):(E2−E1)  Equation (19)E=(7*E2−5*E1)/2  Equation (20)

Now, in this eighth exemplary embodiment, because the pre-specifiednumber that is applied is the number 2, the durations E1 and E2 arecalculated in step 215A, but this is not to be limiting. For example,the pre-specified number that is applied may be the number 3. In such acase, as an example, a duration E3 is calculated in step 215A inaddition to the durations E1 and E2. The duration E3 is a total ofdurations (T2, T3, T4 and T5) representing detection intervals of thepre-specified number of pulse reversals (T2 to T5). Thus, thepre-specified number may be any number as long as it is at least 2.

In step 221A in the eighth exemplary embodiment, the speed relating torotation of the image forming drum 44 is calculated on the basis of thepre-specified number of total durations E1 and E2 and the referencerotation angle θ₀, but this is not to be limiting. For example, thepre-specified number that is applied may be 3, the durations E1 to E3may be calculated in step 215A, and the speed relating to rotation ofthe image forming drum 44 may be calculated in step 221A on the basis ofany two of the durations E1, E2 and E3 and the reference rotation angleθ₀.

The pre-specified number that is applied may be the number 4, withdurations E1 to E4 being calculated in step 215A (E4 being the sum ofdurations T3 to T6), and the speed relating to rotation of the imageforming drum 44 being calculated in step 221A on the basis of an averagevalue E1′ of E1 and E2, an average value E2′ of E3 and E4, and thereference rotation angle θ₀. Thus, the speed relating to rotation of theimage forming drum 44 may be calculated in step 221A on the basis of theplural durations obtained by calculation in step 215A and the referencerotation angle θ₀.

In the eighth exemplary embodiment, the calculation componentcorresponds to the processing of step 215A and the estimation componentcorresponds to the processing of step 221A.

Ninth Exemplary Embodiment

Next, a ninth exemplary embodiment will be described. Portions of thisninth exemplary embodiment that are the same as in the seventh andeighth exemplary embodiments are assigned the same reference numeralsand will not be described.

In the seventh exemplary embodiment, an example is described in whichthe programs for executing the processing of the flowchart shown in FIG.21 and the processing of the flowchart shown in FIG. 22 are memorized inadvance in the ROM 72, the CPU 70 reads a program from the ROM 72 andexecutes the processing of the flowchart shown in FIG. 21, and the FPGA79 reads a program from the ROM 72 and executes the processing of theflowchart shown in FIG. 22. In the ninth exemplary embodiment, an imageformation control processing program for executing the processing of aflowchart shown in FIG. 24 and a speed estimation processing program forexecuting the processing of a flowchart shown in FIG. 25 are memorizedin advance in the ROM 72, the CPU 70 reads a program from the ROM 72 andexecutes the processing of the flowchart shown in FIG. 24, and the FPGA79 reads a program from the ROM 72 and executes the processing of theflowchart shown in FIG. 24 and FIG. 25.

Now the image formation control processing relating to the ninthexemplary embodiment that is executed by the CPU 70 will be describedreferring to FIG. 24. FIG. 24 is a flowchart illustrating a flow ofprocessing of the image formation control processing program that isexecuted by the FPGA 79 when an instruction to start execution of theimage formation control processing relating to the ninth embodiment isinputted. In the image forming device 10 relating to the ninth exemplaryembodiment, the image formation control processing program is memorizedin advance at the ROM 72 serving as a storage medium, but this is not tobe limiting. Modes may be employed in which the image formation controlprocessing program is provided having been saved on a storage mediumreadable by a computer, such as a CD-ROM, DVD-ROM, USB memory or thelike, and modes may be employed in which the program is distributedthrough a communications component, by wire or by wireless. Steps inFIG. 24 that carry out processing the same as in the flowchart shown inFIG. 21 are assigned the same step numbers as in FIG. 21 anddescriptions thereof will not be given. The description starts from step100A.

In step 100A of FIG. 24, an instruction to start execution of the speedestimation processing relating to the ninth exemplary embodiment isoutputted to the FPGA 79. Hence, the FPGA 79 performs control so as tostart execution of the speed estimation processing relating to the ninthexemplary embodiment.

Now the speed estimation processing relating to the ninth exemplaryembodiment that is executed by the FPGA 79 of the ninth exemplaryembodiment will be described referring to FIG. 25. FIG. 25 is aflowchart illustrating a flow of processing of the speed estimationprocessing program that is executed by the FPGA 79 when an instructionto start execution of the speed estimation processing relating to theninth exemplary embodiment is inputted. In the image forming device 10relating to the ninth exemplary embodiment, the speed estimationprocessing program is memorized in advance at the ROM 72 serving as astorage medium, but this is not to be limiting. Modes may be employed inwhich the speed estimation processing program is provided having beensaved on a storage medium readable by a computer, such as a CD-ROM,DVD-ROM, USB memory or the like, and modes may be employed in which theprogram is distributed through a communications component, by wire or bywireless. Steps in FIG. 25 that carry out processing the same as in theflowchart shown in FIG. 22 are assigned the same step numbers as in FIG.22 and descriptions thereof will not be given. Steps that differ fromthe steps of the flowchart shown in FIG. 22 will be described here.

In step 201A of FIG. 25, the rotation angle θ₀ is read from the ROM 72.Then the processing advances to step 202A.

In step 216A, if it is judged that all the values of variable T0,variable T1, variable T2 and variable T3 are greater than zero, (whenthe judgement is positive) it is determined that information that willbe required when estimating a speed in step 230A, details of which aredescribed below, is all present, after which the processing advances tostep 230A.

In step 230A, a speed relating to rotation of the image forming drum 44is estimated by calculation on the basis of the total duration E1calculated in the earlier-described step 214A and the reference rotationangle θ₀. More specifically, in step 230A, an angular speed W of theimage forming drum 44 is calculated by dividing the reference rotationangle θ₀ by the duration E1, as in equation (8).

Then, in step 232A, the value of the angular speed W calculated in step230A is outputted (reported) to the CPU 70. Then the processing advancesto step 222A.

Now the description of the flowchart shown in FIG. 24 is resumed. In thenext step 103A, it is determined whether or not a value of the angularspeed W has been received from the FPGA 79. The determination processingof step 103A is repeated until reception is determined. When receptionis determined in step 103A, the processing advances to the next step105A.

Then, in step 105A, the distance R₀ and the distance X₀ are read fromthe ROM 72, the angular speed W estimated in the above speed estimationprocessing is used to calculate, with equation (9), a period P of theclock signal that prescribes timings of ejections of ink droplets fromthe nozzles 48 a, the period of the clock signal is corrected by settingthis period P as a new period of the clock signal to be used whenejecting ink droplets from the nozzles 48 a, after which the processingadvances to the next step 106A.

In the ninth exemplary embodiment, the estimation component correspondsto the processing of step 230A and the correction component correspondsto the processing of step 105A.

Tenth Exemplary Embodiment

Next, a tenth exemplary embodiment will be described. Portions of thistenth exemplary embodiment that are the same as in the seventh to ninthexemplary embodiments are assigned the same reference numerals and willnot be described.

In the tenth exemplary embodiment, the image formation controlprocessing program for executing the processing of the flowchart shownin FIG. 24 and the speed estimation processing program for executingprocessing of a flowchart shown in FIG. 26 are memorized in the ROM 72in advance, the CPU 70 reads a program from the ROM 72 and executes theprocessing of the flowchart shown in FIG. 24, and the FPGA 79 reads aprogram from the ROM 72 and executes the processing of the flowchartshown in FIG. 26.

Now the speed estimation processing that is executed by the FPGA 79 ofthe tenth exemplary embodiment will be described referring to FIG. 26.FIG. 26 is a flowchart illustrating a flow of processing of the speedestimation processing program that is executed by the FPGA 79 when aninstruction to start execution of the speed estimation processingrelating to the tenth exemplary embodiment is inputted. In the imageforming device 10 relating to the tenth exemplary embodiment, the speedestimation processing program is memorized in advance at the ROM 72serving as a storage medium, but this is not to be limiting. Modes maybe employed in which the speed estimation processing program is providedhaving been saved on a storage medium readable by a computer, such as aCD-ROM, DVD-ROM, USB memory or the like, and modes may be employed inwhich the program is distributed through a communications component, bywire or by wireless.

Step 201A of FIG. 26 is the same as in the processing of the flowchartshown in FIG. 25, and steps 202A, 204A, 207A, 208A, 210A, 212A, 215A,217A, 219A and 222A are the same as in the processing of the flowchartshown in FIG. 23, so will not be described.

In the tenth exemplary embodiment, after the processing of step 219Aends, the processing advances to step 240A. In step 240A, a speedrelating to rotation of the image forming drum 44 is estimated bycalculation on the basis of the pre-specified number of total durationsE1 and E2 that have been memorized in the NVM 76 and the referencerotation angle θ₀. More specifically, similarly to the eighth exemplaryembodiment, in step 240A a duration E, for estimating the speed relatingto rotation of the image forming drum 44 that is to be estimated a nexttime (the angular speed W of the image forming drum 44 in this tenthexemplary embodiment), is estimated by linear extrapolation, based onthe pre-specified number of the total durations E1 and E2 memorized inthe NVM 76, and the angular speed W of the image forming drum 44 isestimated by dividing the reference rotation angle θ₀ by the duration E,as in equation (10). Then the processing advances to step 242A.

In step 242A, the value of the angular speed W calculated in step 240Ais outputted (reported) to the CPU 70. Then the processing advances tostep 222A and subsequent processing the same as in the eighth exemplaryembodiment is carried out.

In the tenth exemplary embodiment, the estimation component correspondsto the processing of step 240A.

Eleventh Exemplary Embodiment

Next, an eleventh exemplary embodiment will be described. Portions ofthis eleventh exemplary embodiment that are the same as in the seventhto tenth exemplary embodiments are assigned the same reference numeralsand will not be described.

In the eleventh exemplary embodiment, the image formation controlprocessing program for executing the processing of the flowchart shownin FIG. 21 and the speed estimation processing program for executingprocessing of a flowchart shown in FIG. 27 are memorized in the ROM 72in advance, the CPU 70 reads a program from the ROM 72 and executes theprocessing of the flowchart shown in FIG. 21, and the FPGA 79 reads aprogram from the ROM 72 and executes the processing of the flowchartshown in FIG. 27.

Now the speed estimation processing that is executed by the FPGA 79 ofthe eleventh exemplary embodiment will be described referring to FIG.27. FIG. 27 is a flowchart illustrating a flow of processing of thespeed estimation processing program that is executed by the FPGA 79 whenan instruction to start execution of the speed estimation processingrelating to the eleventh exemplary embodiment is inputted. In the imageforming device 10 relating to the eleventh exemplary embodiment, thespeed estimation processing program is memorized in advance at the ROM72 serving as a storage medium, but this is not to be limiting. Modesmay be employed in which the speed estimation processing program isprovided having been saved on a storage medium readable by a computer,such as a CD-ROM, DVD-ROM, USB memory or the like, and modes may beemployed in which the program is distributed through a communicationscomponent, by wire or by wireless.

Steps 200A, 202A, 204A, 208A, 210A, 212A, 214A, 216A and 222A of FIG. 27are the same as in the processing of the flowchart shown in FIG. 22, sowill not be described.

When the judgement in step 204A of FIG. 27 is positive, the processingadvances to step 250A. In step 250A, variables—a variable i, a variableT0, a variable T1, a variable T2, a variable T3, a variable E1, avariable V1 and a variable V2—are initialized by setting the values ofthe variables to zero, and the processing advances to step 208A.

When the judgement in step 216A is positive, the processing advances tostep 252A. In step 252A, a speed V_(k) relating to rotation of the imageforming drum 44 is estimated on the basis of the total duration E1 andthe reference rotation angle θ₀. More specifically, in step 252A, theouter periphery speed V_(k) of the image forming drum 44 is estimated bydividing the movement distance (R₀θ₀) of the outer peripheral face ofthe image forming drum 44 through the reference rotation angle θ₀ by thetotal duration E1, as in equation (13).

Then, in step 254A, the value of variable V1 is updated by putting thevalue of variable V2 into variable V1, and the value of variable V2 isupdated by putting the value of variable V_(k) into variable V2.

Next, in step 256A, by judging whether or not all the values of variableV1 and variable V2 are greater than zero, it is determined whether ornot information that will be required when estimating a speed in step258A, details of which are described below, is all present.

In step 256A, if it is judged that there is a variable among all thevariables of variable V1 and variable V2 whose value is zero, it isdetermined that not all the information that would be required whenestimating the speed in step 258A whose details are described below ispresent, and the processing returns to step 208A. On the other hand, ifit is judged in step 256A that the values of all the variables ofvariable V1 and variable V2 are greater than zero, it is determined thatall the information that will be required when estimating the speed instep 258A whose details are described below is present, and theprocessing advances to the next step 258A.

In step 258A, a speed relating to rotation of the image forming drum 44subsequent to the speed relating to rotation of the image forming drum44 that has been estimated in step 252A at the current time isestimated, by linear extrapolation on the basis of the pre-specifiednumber (two in the eleventh exemplary embodiment) of speeds relating torotation of the image forming drum 44 (outer periphery speeds in theeleventh exemplary embodiment), as in equation (14). More specifically,in step 258A, an outer periphery speed V of the image forming drum 44subsequent to the outer periphery speed V_(k) of the image forming drum44 that has been estimated for the current time in step 252A isestimated by calculation, on the basis of the pre-specified number ofouter periphery speeds V1 and V2, as in equation (14). In step 258A, theouter periphery speed V may instead be estimated as in equation (15).

Then, in step 260A, the value of the outer periphery speed V calculatedin step 258A is outputted (reported) to the CPU 70. Then the processingadvances to step 222A.

In the eleventh exemplary embodiment, a first speed estimation sectioncorresponds to the processing of step 252A and a second speed estimationsection corresponds to the processing of step 258A.

Twelfth Exemplary Embodiment

Next, a twelfth exemplary embodiment will be described. Portions of thistwelfth exemplary embodiment that are the same as in the seventh toeleventh exemplary embodiments are assigned the same reference numeralsand will not be described.

In the twelfth exemplary embodiment, the image formation controlprocessing program for executing the processing of the flowchart shownin FIG. 24 and a speed estimation processing program for executingprocessing of a flowchart shown in FIG. 28 are memorized in the ROM 72in advance, the CPU 70 reads a program from the ROM 72 and executes theprocessing of the flowchart shown in FIG. 24, and the FPGA 79 reads aprogram from the ROM 72 and executes the processing of the flowchartshown in FIG. 28.

Now the speed estimation processing that is executed by the FPGA 79 ofthe twelfth exemplary embodiment will be described referring to FIG. 28.FIG. 28 is a flowchart illustrating a flow of processing of the speedestimation processing program that is executed by the FPGA 79 when aninstruction to start execution of the speed estimation processingrelating to the twelfth exemplary embodiment is inputted. In the imageforming device 10 relating to the twelfth exemplary embodiment, thespeed estimation processing program is memorized in advance at the ROM72 serving as a storage medium, but this is not to be limiting. Modesmay be employed in which the speed estimation processing program isprovided having been saved on a storage medium readable by a computer,such as a CD-ROM, DVD-ROM, USB memory or the like, and modes may beemployed in which the program is distributed through a communicationscomponent, by wire or by wireless.

Steps 201A, 202A, 204A, 208A, 210A, 212A, 214A, 216A and 222A of FIG. 28are the same as in the processing of the flowchart shown in FIG. 25, sowill not be described.

When the judgement in step 204A of FIG. 28 is positive, the processingadvances to step 261A. In step 261A, variables—a variable i, a variableT0, a variable T1, a variable T2, a variable T3, a variable E1, avariable W1 and a variable W2—are initialized by setting the values ofthe variables to zero, and the processing advances to step 208A.

When the judgement in step 216A is positive, the processing advances tostep 262A. In step 262A, a speed W_(k) relating to rotation of the imageforming drum 44 is estimated on the basis of the total duration E1 andthe reference rotation angle θ₀. More specifically, in step 262A, theouter periphery speed V_(k) of the image forming drum 44 is estimated bydividing the reference rotation angle θ₀ by the total duration E1, as inequation (16).

Then, in step 264A, the value of variable W1 is updated by putting thevalue of variable W2 into variable W1, and the value of variable W2 isupdated by putting the value of variable W_(k) into variable W2.

Next, in step 266A, by judging whether or not all the values of variableW1 and variable W2 are greater than zero, it is determined whether ornot information that will be required when estimating a speed in step268A, details of which are described below, is all present.

In step 266A, if it is judged that there is a variable among all thevariables of variable W1 and variable W2 whose value is zero, it isdetermined that not all the information that would be required whenestimating the speed in step 268A whose details are described below ispresent, and the processing returns to step 208A. On the other hand, ifit is judged in step 266A that the values of all the variables ofvariable W1 and variable W2 are greater than zero, it is determined thatall the information that will be required when calculating the speed instep 268A whose details are described below is present, and theprocessing advances to the next step 268A.

In step 268A, a speed relating to rotation of the image forming drum 44subsequent to the speed W_(k) relating to rotation of the image formingdrum 44 that has been estimated in step 262A at the current time isestimated, on the basis of the pre-specified number (two in the twelfthexemplary embodiment) of speeds relating to rotation of the imageforming drum 44 (angular speeds in the twelfth exemplary embodiment), asin equation (17). More specifically, in step 268A, an angular speed W ofthe image forming drum 44 subsequent to the angular speed W_(k) that hasbeen estimated for the current time in step 262A is estimated bycalculation, on the basis of the pre-specified number of angular speedsW1 and W2, as in equation (17). In step 268A, the outer angular speed Wmay instead be estimated as in equation (18).

Then, in step 270A, the value of the angular speed W calculated in step268A is outputted (reported) to the CPU 70. Then the processing advancesto step 222A.

In the twelfth exemplary embodiment, the first speed estimation sectioncorresponds to the processing of step 262A and the second speedestimation section corresponds to the processing of step 268A.

In the seventh to twelfth exemplary embodiments, examples are presentedand described in which a speed (the outer periphery speed V or theangular speed W) relating to rotation of the image forming drum 44,which serves as the rotating body in the image forming device 10 withthe structure illustrated in FIG. 1, is estimated, and the period P ofthe clock signal is corrected in accordance with the estimated speed.However, this is not to be limiting. For example, in the image formingdevice 312 as illustrated in FIG. 18, a conveyance speed of theconveyance belt 328 may be estimated, by estimating a speed (an outerperiphery speed or an angular speed) of the driving roller 324, whichserves as the rotating body, and correcting a period P of a clock signalin accordance with the estimated conveyance speed.

Furthermore, in the above-described seventh and ninth exemplaryembodiments, examples have been presented in which the speed relating torotation of the rotating body is estimated using the duration E1.However, this is not to be limiting. For example, the durations E1 andE2 may be calculated as described in the eighth exemplary embodiment andan outer periphery speed V (or angular speed W) that is the speedrelating to rotation of the rotating body may be estimated using anaverage value of the durations E1 and E2. Thus, the speed relating torotation of the rotating body may be estimated using an average value ofa pre-specified number of durations.

In the seventh to twelfth exemplary embodiments described above,examples have been presented and described in which, each time a pulsereversal is detected, a total duration representing a detection intervalof a pre-specified number of pulse reversals, which is a number of pulsereversals of the pulse signals generated by the rotary encoder 52 inassociation with rotation of the image forming drum 44 through thereference rotation angle θ₀, prior to the current detection iscalculated. However, this is not to be limiting. For example, each timea pulse reversal is detected, a duration required for detecting fourpulse signal reversals over phase A and phase B prior to the currentdetection may be calculated on the basis of the detection intervals ofthe pulse signal reversals. In this case, the speed relating to rotationof the rotating body is estimated on the basis of the calculatedduration and a rotation angle required for four reversals of the pulsesignals over the phases. Further, in a case in which pulse signals inthree phases or more are generated by the rotary encoder 52, a durationrequired for detecting six pulse signal reversals over phase A and phaseB prior to the current detection may be calculated on the basis of thedetection intervals of the pulse signal reversals. In this case, thespeed relating to rotation of the rotating body is estimated on thebasis of the calculated duration and a rotation angle required for sixreversals of the pulse signals over the respective phases.

Thus, each time a pulse reversal is detected, a duration required fordetecting a pre-specified number of pulse signal reversals over thephases prior to the current detection may be calculated on the basis ofthe detection intervals of the pulse signal reversals, and the speedrelating to rotation of the rotating body may be estimated on the basisof the calculated duration and a rotation angle required for thepre-specified number of reversals of the pulse signals over the phases.

In the seventh to twelfth exemplary embodiments, examples are presentedand described in which, by the speed estimation processing, processingis executed that estimates a speed relating to rotation of the imageforming drum 44 and, by the image formation control processing,processing is executed that corrects the period P of the clock signal inaccordance with the estimated speed. However, this is not to belimiting. Instead of processing that corrects the period P of the clocksignal, processing may be executed in the image formation controlprocessing that, by reference to the estimated speed, controls rotarydriving of the image forming drum 44 via the motor controller 86 suchthat the outer periphery speed of the image forming drum 44 is at apre-specified outer periphery speed.

In the seventh to twelfth exemplary embodiments, examples are presentedand described in which a speed relating to rotation of the rotating bodyis estimated by calculation using an arithmetic equation. However, thisis not to be limiting. For example, as a variant example of the seventhexemplary embodiment, a variant example may be presented in which atable—in which the duration E1, the distance R₀ and the referencerotation angle θ₀ are inputs and the outer periphery speed V is theoutput—is memorized in advance at a storage medium, such as the ROM 72or the like, and the outer periphery speed V is estimated by derivationusing this table. In the above described eighth to twelfth exemplaryembodiments too, a table in which the values required for calculation ofthe speed relating to rotation of the rotating body are the inputs andthe speed relating to rotation of the rotating body is the output may bememorized in advance at a storage medium such as the ROM 72 or the like,and the speed relating to rotation of the rotating body may be estimatedby derivation using this table. Furthermore, a table in which the speedrelating to rotation of the rotating body and the distance X₀ betweenthe centers of neighboring dots are the inputs and the period P of theclock signal is the output may be memorized in advance at a storagemedium such as the ROM 72 or the like, and the period P of the clocksignal may be derived using this table.

In the seventh to twelfth exemplary embodiments, examples are presentedand described of image forming devices of modes in which images aredirectly formed on recording paper W by the inkjet recording heads 48.However, this is not to be limiting. Image forming devices of modes thatform images on recording paper W via intermediate transfer bodies arealso possible. As an example of such cases, there is an image formingdevice of a mode in which a latent image is formed on an outerperipheral face (the pre-specified surface) of a photosensitive drum,which is the rotating body, by recording heads that are provided withlight-emitting elements such as LEDs (light-emitting diodes) or thelike, the latent image is converted to a toner image, and the tonerimage is transferred onto a recording face (surface) of recording paper.

In the seventh to twelfth exemplary embodiments, the inkjet recordingheads 48 are constituted with the plural nozzles 48 a being lined up intwo rows without overlapping in the sub-scanning direction. However,this is not to be limiting. The constitution of the inkjet recordingheads 48 may be any constitution as long as the plural nozzles 48 a aretwo-dimensionally arranged without overlapping in the sub-scanningdirection.

In the exemplary embodiments described above, the distance R₀ isinvariable, but this is not to be limiting and the distance R₀ may bevariable. In such a case, a variant example may be mentioned in whichthe distance R₀ is altered in accordance with the thickness of therecording paper W at which an image is to be formed.

In the exemplary embodiments described above, transmission-typephotosensors detect light amount variations and generate pulse signalsin accordance with the light amount variations, but this is not to belimiting. For example, reflective plates with a greater opticalreflectivity than other regions of the code wheel 53 may be providedinstead of the slits 53A, and a reflection-type photosensor may be usedinstead of a transmission-type photosensor. The reflection-typephotosensor is structured with a light-emitting element and a lightdetection element that detects light which has been emitted from thelight-emitting element and reflected at the reflection plates. Thus,light amount variations may be detected and pulse signals generated bythe reflection-type photosensor. Further, magnets may be providedinstead of the slits 53A and, using a magnetism sensor instead of aphotosensor, variations in magnetism may be detected and pulsesgenerated by the magnetism sensor.

Thus, the rotary encoder 52 may be constituted to include: pluraldetected portions that are arranged at the code wheel 53 with equalspacings along the circumferential direction, and that are structuredsuch that a particular physical characteristic thereof has a differenceof at least a pre-specified magnitude from other regions of the codewheel 53; and a pulse signal generation portion that, in associationwith rotation of the code wheel 53, detects the difference in magnitudeof the particular physical characteristic between the plural detectedportions and regions of the code wheel 53 other than the detectedportions and generates a pulse signal in accordance with the detecteddifference.

In the exemplary embodiments described above, examples have beenpresented and described of cases in which the image formation controlprocessing program is executed by the CPU 70 and the speed estimationprocessing program is executed by the FPGA 79. However, this is not tobe limiting. The image formation control processing program and thespeed estimation processing program may both be executed by the CPU 70.

1. A speed calculation device for a printing apparatus including inkjetrecording heads that serve as plural image forming elements, the devicecomprising: a rotary encoder that generates a plurality of pulse signalswith different phases in accordance with rotation of an image formingdrum; a detection component that detects rises and falls of respectivepulses of the plurality of pulse signals generated by the rotaryencoder; a duration calculation component that, each time a rise or fallis detected by the detection component, calculates a total duration of apre-specified first number of durations representing detection intervalsof rises or falls detected prior to the rise or fall currently detectedby the detection component; and a speed calculation component thatincludes a speed detection section that detects a speed relating torotation of the image forming drum on the basis of the total durationand a rotation angle of the image forming drum that corresponds to onepulse of the pulse signals, and a speed calculation section that, aftera pre-specified number of speeds have been detected by the speeddetection section, calculates by estimation, on the basis of apre-specified second number of the speeds relating to rotation of theimage forming drum that have been detected by the speed detectionsection, the speed relating to rotation of the rotating body that is tobe detected subsequent to the speed relating to rotation of the rotatingbody currently detected by the speed detection section, to output aclock signal whereby the image forming elements form dots thatrespectively constitute an image at a predetermined surfacesynchronously with the clock signal.
 2. A storage medium readable by acomputer, the storage medium storing a program for causing a computer tofunction as: a detection component that detects rises and falls ofrespective pulses of a plurality of pulse signals generated by a rotaryencoder, which generates the plurality of pulse signals with differentphases in accordance with rotation of an image forming drum of aprinting apparatus including inkjet recording heads that serve as pluralimage forming elements; a duration calculation component that, each timea rise or fall is detected by the detection component, calculates atotal duration of a pre-specified first number of durations representingdetection intervals of rises or falls detected by the detectioncomponent prior to the current rise or fall detected by the detectioncomponent; and a speed calculation component that includes a speeddetection section that detects a speed relating to rotation of the imageforming drum on the basis of the total duration and a rotation angle ofthe image forming drum that corresponds to one pulse of the pulsesignals, and a speed calculation section that, after a pre-specifiednumber of speeds have been detected by the speed detection section,calculates by estimation, on the basis of a pre-specified second numberof the speeds relating to rotation of the image forming drum that havebeen detected by the speed detection section, the speed relating torotation of the image forming drum that is to be detected subsequent tothe speed relating to rotation of the image forming drum currentlydetected by the speed detection section, to output a clock signalwhereby the image forming elements form dots that respectivelyconstitute an image at a predetermined surface synchronously with theclock signal.
 3. A speed estimation device for a printing apparatusincluding inkjet recording heads that serve as plural image formingelements, the device comprising: an image forming drum provided with aplurality of detected portions that are arranged along a rotationdirection with a pre-specified rotation angle spacing; a rotary encoderthat generates a plurality of pulse signals with different phases inaccordance with passing of each of the plurality of detected portions inassociation with rotation of the image forming drum; a detectioncomponent that detects reversals of the pulse signals generated by therotary encoder; a calculation component that, each time a reversal isdetected by the detection component, calculates a duration required fordetecting a pre-specified number of reversals of the pulse signals overthe respective phases prior to the current detection, on the basis ofintervals of detection of the reversals; and an estimation componentthat estimates a speed relating to rotation of the image forming drum onthe basis of the duration calculated by the calculation component and areference rotation angle, which is a rotation angle required for thepre-specified number of reversals of the pulse signals over therespective phases, to output a clock signal whereby the image formingelements form dots that respectively constitute an image at apredetermined surface synchronously with the clock signal.
 4. The speedestimation device of claim 3, wherein the estimation component estimatesan angular speed of the rotating body, by calculating a ratio of thereference rotation angle to the duration calculated by the calculationcomponent.
 5. The speed estimation device of claim 3, wherein theestimation component estimates a linear speed at a position separated bya pre-specified distance in a rotation radial direction from a center ofthe rotating body, by calculating a ratio of a movement distancecorresponding to the reference rotation angle at the position separatedby the pre-specified distance in the rotation radial direction from thecenter of the rotating body to the duration calculated by thecalculation component.
 6. A speed estimation device for a printingapparatus including inkjet recording heads that serve as plural imageforming elements, the device comprising: an image forming drum providedwith a plurality of detected portions that are arranged along a rotationdirection with a pre-specified rotation angle spacing; a rotary encoderthat generates a plurality of pulse signals with different phases inaccordance with passing of each of the plurality of detected portions inassociation with rotation of the image forming drum; a detectioncomponent that detects reversals of the pulse signals generated by therotary encoder; a calculation component that, each time a reversal isdetected by the detection component, calculates a duration required fordetecting a pre-specified number of reversals of the pulse signals overthe respective phases prior to the current detection, on the basis ofintervals of detection of the reversals; and an estimation componentthat estimates a speed relating to rotation of the image forming drum onthe basis of a plurality of the duration calculated by the calculationcomponent and a reference rotation angle, which is a rotation anglerequired for the pre-specified number of reversals of the pulse signalsover the respective phases, to output a clock signal whereby the imageforming elements form dots that respectively constitute an image at apredetermined surface synchronously with the clock signal.
 7. The speedestimation device of claim 6, wherein the estimation component estimatesthe duration to be calculated by the calculation component a next time,on the basis of the plurality of durations, and estimates the speedrelating to rotation of the rotating body on the basis of the estimatedduration and the reference rotation angle.
 8. The speed estimationdevice of claim 7, wherein the estimation component estimates theduration to be calculated by the calculation component the next time, onthe basis of the plurality of durations, and estimates an angular speedof the rotating body, by calculating a ratio of the reference rotationangle to the estimated duration.
 9. The speed estimation device of claim7, wherein the estimation component estimates the duration to becalculated by the calculation component the next time, on the basis ofthe plurality of durations, and estimates a linear speed at a positionseparated by a pre-specified distance in a rotation radial directionfrom a center of the rotating body, by calculating a ratio of a movementdistance corresponding to the reference rotation angle at the positionseparated by the pre-specified distance in the rotation radial directionfrom the center of the rotating body to the estimated duration.
 10. Thespeed estimation device of claim 6, wherein the plurality of durationsis two durations, being the duration calculated by the calculationcomponent at a current time and the duration calculated by thecalculation component at a previous time.
 11. A speed estimation devicefor a printing apparatus including inkjet recording heads that serve asplural image forming elements, the device comprising: an image formingdrum provided with a plurality of detected portions that are arrangedalong a rotation direction with a pre-specified rotation angle spacing;a rotary encoder that generates a plurality of pulse signals withdifferent phases in accordance with passing of each of the plurality ofdetected portions in association with rotation of the image formingapparatus; a detection component that detects reversals of the pulsesignals generated by the rotary encoder; a calculation component that,each time a reversal is detected by the detection component, calculatesa duration required for detecting a pre-specified number of reversals ofthe pulse signals over the respective phases prior to the currentdetection, on the basis of intervals of detection of the reversals; andan estimation component provided with a first speed estimation sectionthat estimates a speed relating to rotation of the image forming drum onthe basis of the duration calculated by the calculation component and areference rotation angle, which is a rotation angle required for thepre-specified number of reversals of the pulse signals over therespective phases, and a second speed estimation section that, after aplurality of the speed have been estimated by the first speed estimationsection, estimates the speed relating to rotation of the image formingdrum subsequent to the speed estimated by the first speed estimationsection at the current time, on the basis of the plurality of estimatedspeeds, to output a clock signal whereby the image forming elements formdots that respectively constitute an image at a predetermined surfacesynchronously with the clock signal.
 12. The speed estimation device ofclaim 11, wherein the first speed estimation section estimates anangular speed of the rotating body, by calculating a ratio of thereference rotation angle to the duration calculated by the calculationcomponent, and the second speed estimation section, after a plurality ofthe angular speed have been estimated by the first speed estimationsection, estimates an angular speed relating to rotation of the rotatingbody subsequent to the angular speed estimated by the first speedestimation section at the current time, on the basis of the plurality ofestimated angular speeds.
 13. The speed estimation device of claim 11,wherein the first speed estimation section estimates a linear speed at aposition separated by a pre-specified distance in a rotation radialdirection from a center of the rotating body, by calculating a ratio ofa movement distance corresponding to the reference rotation angle at theposition separated by the pre-specified distance in the rotation radialdirection from the center of the rotating body to the durationcalculated by the calculation component, and the second speed estimationsection, after a plurality of the linear speed have been estimated bythe first speed estimation section, estimates a linear speed at theposition separated by the pre-specified distance in the rotation radialdirection from the center of the rotating body subsequent to the linearspeed estimated by the first speed estimation section at the currenttime, on the basis of the plurality of estimated linear speeds.
 14. Astorage medium readable by a computer, the storage medium storing aprogram of instructions executable by the computer to perform afunction, the function comprising: in association with rotation of animage forming drum of a printing apparatus including inkjet recordingheads that serve as plural image forming elements, the image formingdrum being provided with a plurality of detected portions that arearranged along a rotation direction with a pre-specified rotation anglespacing, detecting reversals of pulse signals generated by a rotaryencoder that generates a plurality of the pulse signals with differentphases in accordance with passing of each of the plurality of detectedportions; each time a reversal is detected, calculating a durationrequired for detecting a pre-specified number of reversals of the pulsesignals over the respective phases prior to the current detection, onthe basis of intervals of detection of the reversals; and estimating aspeed relating to rotation of the image forming drum on the basis of thecalculated duration and a reference rotation angle, which is a rotationangle required for the pre-specified number of reversals of the pulsesignals over the respective phases, to output a clock signal whereby theimage forming elements form dots that respectively constitute an imageat a predetermined surface synchronously with the clock signal.
 15. Astorage medium readable by a computer, the storage medium storing aprogram of instructions executable by the computer to perform afunction, the function comprising: in association with rotation of animage forming drum an of a printing apparatus including inkjet recordingheads that serve as plural image forming elements, the image formingdrum being provided with a plurality of detected portions that arearranged along a rotation direction with a pre-specified rotation anglespacing, detecting reversals of pulse signals generated by a rotaryencoder that generates a plurality of the pulse signals with differentphases in accordance with passing of each of the plurality of detectedportions; each time a reversal is detected, calculating a durationrequired for detecting a pre-specified number of reversals of the pulsesignals over the respective phases prior to the current detection, onthe basis of intervals of detection of the reversals; and estimating aspeed relating to rotation of the image forming drum on the basis of aplurality of the calculated duration and a reference rotation angle,which is a rotation angle required for the pre-specified number ofreversals of the pulse signals over the respective phases, to output aclock signal whereby the image forming elements form dots thatrespectively constitute an image at a predetermined surfacesynchronously with the clock signal.
 16. A storage medium readable by acomputer, the storage medium storing a program of instructionsexecutable by the computer to perform a function, the functioncomprising: in association with rotation of an image forming drum of aprinting apparatus including inkjet recording heads that serve as pluralimage forming elements, the image forming drum being provided with aplurality of detected portions that are arranged along a rotationdirection with a pre-specified rotation angle spacing, detectingreversals of pulse signals generated by a rotary encoder that generatesa plurality of the pulse signals with different phases in accordancewith passing of each of the plurality of detected portions; each time areversal is detected, calculating a duration required for detecting apre-specified number of reversals of the pulse signals over therespective phases prior to the current detection, on the basis ofintervals of detection of the reversals; estimating a speed relating torotation of the image forming drum on the basis of the calculatedduration and a reference rotation angle, which is a rotation anglerequired for the pre-specified number of reversals of the pulse signalsover the respective phases; and after a plurality of the speed have beenestimated, estimating the speed relating to rotation of the imageforming drum subsequent to the speed estimated at the current time, onthe basis of the plurality of estimated speeds, to output a clock signalwhereby the image forming elements form dots that respectivelyconstitute an image at a predetermined surface synchronously with theclock signal.